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Prosociality and Negative Emotionality Mediate theAssociation of Serotonin Transporter Genotype WithChildhood ADHD and ODDWhitney A. Brammer a & Steve S. Lee aa Department of Psychology , University of California , Los AngelesPublished online: 11 Oct 2013.

To cite this article: Whitney A. Brammer & Steve S. Lee (2013) Prosociality and Negative Emotionality Mediate theAssociation of Serotonin Transporter Genotype With Childhood ADHD and ODD, Journal of Clinical Child & AdolescentPsychology, 42:6, 809-819, DOI: 10.1080/15374416.2013.840638

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Prosociality and Negative Emotionality Mediate theAssociation of Serotonin Transporter Genotype

With Childhood ADHD and ODD

Whitney A. Brammer and Steve S. Lee

Department of Psychology, University of California, Los Angeles

Although there is evidence that the promoter polymorphism of the serotonin transporter(5-HTTLPR) gene is associated with attention-deficit=hyperactivity disorder (ADHD)and oppositional defiant disorder (ODD), the pathways underlying these associationsare largely unknown. Given their theoretical and biological plausibility, we testedwhether individual differences in key temperament dimensions (i.e., prosociality, nega-tive emotionality, daring) constituted potential pathways from 5-HTTLPR to ADHDand ODD. Using a well-characterized sample of 194 six to nine-year-old children withand without ADHD, we utilized multiple mediation procedures with bootstrapping toevaluate prosociality, negative emotionality, and daring as independent mediators of5-HTTLPR with separate parent and teacher ratings of ADHD and ODD. Controllingfor ODD, prosociality and negative emotionality significantly mediated the associationof 5-HTTLPR and parent-reported ADHD. Similarly, controlling for ADHD, prosoci-ality and negative emotionality each uniquely mediated the association of 5-HTTLPRand parent-reported ODD. For teacher-reported ADHD, prosociality significantlymediated the association of 5-HTTLPR (controlling for ODD) whereas controllingfor ODD, negative emotionality significantly mediated the prediction of teacher-reported ODD from 5-HTTLPR. Specifically, the number of 5-HTTLPR long alleleswas inversely associated with prosociality and positively associated with negative emo-tionality; prosociality was inversely associated and negative emotionality was positivelyassociated with ADHD and ODD. We consider the role of temperament in geneticallysensitive designs as well as its potential value in the development and delivery ofeffective interventions.

Attention-deficit=hyperactivity disorder (ADHD),oppositional defiant disorder (ODD), and conduct dis-order (CD), are the most common referral for childmental health services (Kazdin, 1995). Approximately8.7% of 8- to 15-year-old children meet diagnosticcriteria for ADHD (Froehlich et al., 2007) and childrenwith ADHD are 11 times more likely than children with-out ADHD to have comorbid ODD or CD (Angold,Costello, & Erkanli, 1999). Childhood ADHD prospec-tively predicts elevated parent–child conflict, academicproblems (e.g., school dropout), and social dysfunction

(Deault, 2010; Hoza et al., 2005; Kent et al., 2011), evenif ADHD itself improves (Lee, Lahey, Owens, &Hinshaw, 2008). Similarly, children with ODD experi-ence elevated family conflict, poor school performance,and hostile attribution biases (Dodge & Frame, 1982;Greene et al., 2002). Like ADHD, early ODD predictsearly-onset CD, depression, and anxiety disorders(Rowe, Costello, Angold, Copeland, & Maughan, 2010).

Genetic factors are salient to the etiology of ADHD,ODD, and CD: Among a representative sample oftwins, each disorder was highly heritable across multiplemeasures and informants; common genetic factors alsoexplained ODD and CD (Eaves et al., 2000). In ameta-analysis of 51 twin and adoption studies, antisocialbehavior, including ODD and CD, was significantly

Correspondence should be addressed to Steve S. Lee, Department

of Psychology, University of California, Los Angeles, 1285 Franz Hall,

Box 951563, Los Angeles, CA 90095. E-mail: stevelee@psych.ucla.edu

Journal of Clinical Child & Adolescent Psychology, 42(6), 809–819, 2013

Copyright # Taylor & Francis Group, LLC

ISSN: 1537-4416 print=1537-4424 online

DOI: 10.1080/15374416.2013.840638

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heritable and moderated by age and assessment method,underscoring the importance of developmental andmethodological factors (Rhee & Waldman, 2002).Reflecting their empirical independence (Hinshaw, 1987),ADHD is significantly heritable with minor sharedenvironmental influences whereas shared environmentalinfluences are more salient to ODD=CD (Burt, 2009). Insum, because ADHD and ODD reflect distinct causalinfluences, tests of their underlying genetic influences mustproperly consider their frequent comorbidity.

One biomarker implicated in the etiology of ADHDand ODD is the promoter polymorphism of the sero-tonin transporter (5-HTTLPR) gene. A comprehensivereview found that 5-HTTLPR was significantly associa-ted with ADHD (Faraone et al., 2005), and a recentmeta-analysis specified that the long allele increasedsusceptibility to ADHD (Gizer, Ficks, & Waldman,2009).However, the associationof 5-HTTLPRwith respectto ODD=CD is less consistent. For example, childrenheterozygous (i.e., short=long genotype) for 5-HTTLPRexhibited more CD symptoms than youth homozygousfor the long or short variants (Malmberg, Wargelius,Lichtenstein, Oreland, & Larsson, 2008), whereas shortallele homozygosity significantly predicted adolescentCD (Sakai et al., 2006). In contrast, preadolescentshomozygous for the 5-HTTLPR long allele were moreaggressive than youth with other 5-HTTLPR variants(Nobile et al., 2007). One possible source of this inconsist-ency is unmeasured gene-environment interplay, whichmay mask the true association of 5-HTTLPR withaggression. Specifically, because exposure to differentenvironmental conditions may affect gene expression(i.e., Gene�Environment interaction), studies thatignore environmental differences may not detect geneticassociations (Moffitt, Caspi, & Rutter, 2005). Further-more, according to differential susceptibility, genes affectsensitivity to negative and positive environments, andthus both adverse and enriching environmental factorsmay moderate genetic effects (Belsky, Bakermans-Kranenburg, & van IJzendoorn, 2007). Given replicatedevidence that the long allele of 5-HTTLPR is associatedwith childhood ADHD, and the need for more robustlyinterrogating the role of 5-HTTLPRandODD, our studyexplicitly tested the association of 5-HTTLPR withdifferentiated measures of ADHD and ODD.

5-HTTLPR may affect individual differences inADHD and ODD through heightened amygdalaactivity during emotional arousal given that it accountsfor 10% of amygdala activation variance (Hariri et al.,2002; Munafo, Brown, & Hariri, 2008). Although5-HTTLPR is a biologically plausible biomarker forADHD and ODD, the factors that potentiate geneticvariation into these disorders are poorly understood.That is, theoretically and biologically plausible mediat-ing factors underlying the association of 5-HTTLPR

and psychopathology are crucial and largely unknown(Rutter, 2006). Further, the use of putative endopheno-types (i.e., heritable intermediate phenotypes moreproximal to the biological basis of the syndrome) mayimprove statistical power because they are less complex(i.e., fewer genetic and environmental influences) thanexplicit disorders (Doyle et al., 2005; Gottesman &Gould, 2003).

Dimensions of temperament may be an appropriateendophenotype for ADHD and ODD given that theyare heritable, developmentally stable, and prospectivelypredict ADHD, ODD, and many dimensions of childpsychopathology (Bates, Pettit, Dodge, & Ridge, 1998;Kelvin, Goodyer, & Altham, 1996; Lahey et al., 2008;Saudino, 2005). Temperament refers to individual dif-ferences in reactivity and self-regulation that areexpressed via emotionality, motor activity, and attention(Rothbart & Derryberry, 1981). Latent variable model-ing revealed that early novelty-seeking presaged a life-time diagnosis of ADHD (Lynn et al., 2005), andteacher-rated negative emotionality predicted parent-rated ADHD severity in preschool children (Healey,Marks, & Halperin, 2011); moreover, age 3 fear=inhibition inversely predicted adult psychopathic per-sonality (Glenn, Raine, Venables, & Mednick, 2007).Temperament models vary widely, but three key facetswere identified as part of a developmental propensitymodel of child psychopathology: prosociality (i.e.,‘‘sympathetic concern of others, helping and sharing,respect for social rules, and guilt over misdeeds’’), nega-tive emotionality (i.e., ‘‘easily and intensely upset byfrustrations, threats, and losses’’), and daring (i.e.,‘‘daring, brave, and adventurous,’’ and ‘‘sensation-seeking’’; Lahey et al., 2008, p. 795). Notably, thesedimensions were developed and validated for explicituse in studies of psychopathology based on items thatexcluded clear synonyms and antonyms of psychopath-ology symptoms. For example, parent ratings of earlyindividual differences in children’s prosociality (low),negative emotionality (high), and daring (high) prospec-tively predicted parent-reported ODD and CD (Laheyet al., 2008). In a later cross-validation study, youth self-reported prosociality, negative emotionality, and daringsimilarly predicted parent- and youth-reported CD(Lahey, Rathouz, Applegate, Tackett, & Waldman,2010). Moreover, all three dimensions were associatedwith a latent antisocial factor derived from official courtrecords, CD symptoms, and self-reported delinquency,controlling for initial conduct problems (Trentacosta,Hyde, Shaw, &Cheong, 2009). Given their favorable psy-chometric properties and robust associationswithADHDand ODD, there is a strong rationale for using thesetemperament facets as mediators of psychopathology.

Consistent with its hypothesized mediational role,individual differences in temperament are sensitive to

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5-HTTLPR. First, infants homozygous for the 5-HTTLPR short allele exhibited elevated negative emo-tionality and distress at 2 months of age (Auerbachet al., 1999). Elevated negative emotionality and dimin-ished positive emotionality were observed in childrenwith at least one short allele of 5-HTTLPR relative tochildren without the short allele or children with highpositive emotionality (Hayden et al., 2010) and healthyadults homozygous for the 5-HTTLPR short alleleexhibited more prosocial empathic responding as wellas higher sympathetic nervous system activation (i.e.,cardiovascular and electrodermal activity) when theyviewed others in distress relative to adults homozygousfor the 5-HTTLPR long allele (Gyurak et al., 2013).The moderating role of 5-HTTLPR was identified, aspositive maternal expressed emotions predicted youthconduct problems but only in youth with one or moreshort alleles (Sonuga-Barke et al., 2009). Finally, therole of serotonin neurotransmission, negative emotion-ality, and prosociality is suggested in rodent models aswell: Knockout mice homozygous for the serotonintransporter null mutation (–=–) exhibited behaviorsassociated with negative emotionality (e.g., less likelyto transition from a dark compartment to a light one,less likely to explore and more likely to avoid brightlyilluminated areas) and less aggression (i.e., slower toattack intruders and attacked with less frequency)relative to þ=þ control littermates (Holmes, Murphy,& Crawley, 2002; Holmes, Yang, Lesch, Crawley, &Murphy, 2003). Thus, 5-HTTLPR is a biologicallyplausible biomarker for individual differences intemperament.

Despite replicated evidence that temperament facetsare sensitive to serotonin neurotransmission and asso-ciated with ADHD and ODD, few studies have testedwhether they constitute pathways through which geneticvariation contributes to childhood ADHD and ODD(see Martel, Nikolas, Jernigan, Friderici, & Nigg, 2010,for a key exception). We tested whether prosociality,negative emotionality, and daring mediated predictionsof parent and teacher-rated ADHD and ODD from5-HTTLPR in a sample of school-age children. We pre-dicted that carriers of at least one 5-HTTLPR long allelewould inversely predict prosociality and positively pre-dict negative emotionality and daring. We also predictthat prosociality would inversely predict ADHD andODD, whereas negative emotionality and daring wouldpositively predict ADHD and ODD.

METHOD

Participants

One hundred ninety-four 6- to 9-year-old (M¼ 7.4,SD¼ 1.2) children with (n¼ 101) and without ADHD

(n¼ 93) were recruited using advertisements at localschools and in public locations as well as referrals fromlocal mental health service providers and pediatricoffices (Table 1). The sample was ethnically diverse:55.7% Caucasian (n¼ 108), 8.8% Hispanic (n¼ 17),8.8% African American (n¼ 17), 3.1% Asian (n¼ 6),and 23.7% (n¼ 46) Mixed=Other. Participants wererequired to live with at least one biological parent atleast half time, be enrolled in school full-time, and befluent in English. Exclusion criteria for all participantsincluded a Full Scale IQ less than 70 or an autism spec-trum, seizure, or any neurological disorder. ADHD pro-band status was based on a positive diagnosis accordingto a structured diagnostic interview that ascertained allrelevant diagnostic criteria (see below for details onclinical assessment procedures). To avoid recruiting asample of improbably high-functioning youth, non-ADHD comparison children were allowed to meetdiagnostic criteria for any disorder other than ADHD.All participants were recruited, screened, and assessedusing identical procedures.

Procedures

Families who contacted the study completed a telephonescreener to determine their eligibility based on theinclusion and exclusion criteria just listed. Familiesand teachers received rating scales through the mail,and families were invited to the research laboratoryfor in-person assessments. Following signed consent andassent procedures for the parent and child, respectively,

TABLE 1

Means and Percentages for Demographic Variables

Variable ADHDa Non-ADHDb F=v2 P

Age (SD) 7.32 (1.13) 7.44 (1.07) 0.61 .43

% Male 72.00 65.59 0.92 .34

% Caucasian 54.46 56.99 0.13 .72

% Household

Income< $70,000

33.66 30.10 1.09 .30

WISC-IV FSIQ (SD) 105.02 (14.61) 108.76 (16.04) 2.82 .10

Total Teacher-Rated

ADHD Symptoms

6.24 (5.23) 4.36 (5.16) 5.25 <.05

% ODD Diagnosis 46.53 9.68 37.97 <.01

Total Parent-Rated

ODD Symptoms

3.25 (2.40) .96 (1.72) 67.91 <.001

Total Teacher-Rated

ODD Symptoms

1.34 (2.34) .79 (1.76) 2.82 .10

% CD Diagnosis 6.93 0 6.85 <.01

Note: Mean differences evaluated by one-way analysis of variance

or chi-square. ADHD¼ attention deficit=hyperactivity disorder;

WISC-IV¼Wechsler Intelligence Scale for Children–Fourth Edition;

FSIQ¼Full-Scale IQ; ODD¼ oppositional defiant disorder; CD¼conduct disorder.

an¼ 101.bn¼ 93.

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clinical psychology graduate students or B.A.-leveltrained staff assessed children using tests of cognitiveability and academic achievement, whereas a secondtrained member of our research staff interviewed parentsabout their child’s psychopathology. All interviewerswere initially blind to the child’s diagnostic status, butthe blind could not always be maintained given theextensive information collected about the child. Parentswere asked to rate each child based on his or her unme-dicated behavior. Approximately 85% of children wereevaluated without their medication during the in-personassessment. The Institutional Review Board approvedall study procedures.

Measures

Genotype. DNA was extracted from saliva usingDNA Genotek Oragene Self-Collection Kits (DNAGenotek, Inc., Ottawa, CA). The 48-base pair (bp)insertion=deletion polymorphism in the promoter regionof 5-HTTLPR was genotyped using standard primers,which produced fragments of either 484 or 528 bp (Heilset al., 1996). The long variant (528 bp) has approxi-mately 3 times the activity of the shorter promoter(484 bp) with the deletion (Lesch et al., 1996). Thiswas the only genetic variant tested in this study. Becausethe precise mode of transmission for 5-HTTLPR isunknown (i.e., dominant, recessive, heterosis), we separ-ately compared all three genotypes with the followingdistribution: long=long (30%, n¼ 60), short=long (45%,n¼ 88), and short=short (25%, n¼ 46). These frequen-cies did not deviate from Hardy-Weinberg equilibrium,v2(1)¼ 1.5, p¼ .22.

Temperament. The Child and AdolescentDispositions Scale is a parent interview of children’stemperament with items that were explicitly developedfor studies of psychopathology by excluding clearsynonyms or antonyms of psychiatric symptoms (Laheyet al., 2008). Parents used a 4-point Likert scale to rate48 items that yielded three factors: prosociality, negativeemotionality, and daring. Previous studies reportedgood internal consistency, high test–retest reliability,construct validity, and external validity (Lahey et al.,2008; Trentacosta et al., 2009). In this sample, theCronbach alpha was .87, .77, and .79 for the pro-sociality, negative emotionality, and daring factors,respectively.

ADHD and ODD. We administered ADHD andODD modules from the Diagnostic Interview Schedulefor Children, fourth edition (DISC-IV) to each child’sparent (Shaffer, Fisher, Lucas, Dulcan & Schwab-Stone,2000). The DISC-IV is extensively validated and

psychometrically sound. In the DSM-IV Field Trials,test–retest reliability for ADHD from the DISC rangedfrom .51 to .64 (Lahey et al., 1994). Forty-two percent(n¼ 51) of ADHD probands were diagnosed with theInattentive type, 11% (n¼ 13) with the Hyperactive type,and 47% (n¼ 57) as Combined type. However, giventhat the predictive validity of dimensionally ratedADHD and ODD was superior to diagnoses (Fergusson& Horwood, 1995), we used the total number of ADHDand ODD symptoms from the DISC-IV as separatedependent variables. The number of ADHD and ODDsymptoms were significantly correlated (r¼ .58, p<.001) as were the number of inattention and hyperactiv-ity symptoms (r¼ .58, p< .001). The Cronbach alphawas .91 and .84 for the total number of ADHD andODD symptoms, respectively.

Teachers completed the Disruptive BehaviorDisorder Rating Scale (Pelham, Gnagy, Greenslade, &Milich, 1992) and rated 45 items keyed to DSM-IVADHD, ODD, and CD from ‘‘not at all’’ to ‘‘verymuch.’’ Items rated as ‘‘pretty much’’ or ‘‘very much’’were scored as a symptom (Lahey et al., 1994). TheDisruptive Behavior Disorder has good psychometricproperties (e.g., predictive validity; Lahey et al., 2004).Cronbach alphas were .93 for ADHD and .90 forODD in this study.

Data Analytic Procedures

We assessed whether individual differences in prosocial-ity, negative emotionality, and daring mediated theassociation of 5-HTTLPR with separate parent and tea-cher ratings of the number of ADHD and ODD symp-toms. We used a multiple mediator macro (Preacher &Hayes, 2008) with bootstrapping, a statistically powerfulnonparametric resampling procedure (MacKinnon,Krull, & Lockwood, 2000). Bootstrapping samples froma data set k number of times and uses percentages ofthose distributions to calculate confidence intervalsand estimate the indirect effect of mediators. Unlike tra-ditional mediation (Baron & Kenny, 1986), recent devel-opments illustrate that mediation does not require asignificant direct effect of the predictor on the outcome(MacKinnon et al., 2000; Preacher & Hayes, 2008).Reflecting a ‘‘stage sequence’’ framework (Collins,Graham, & Flaherty, 1998), the predictor first influencesthe mediator, followed by an effect on the outcome;thus, evaluation of causal mediation through bootstrap-ping is not continent upon a significant direct effect(Zhao, Lynch, & Chen, 2010), especially when the effectsize of the predictor is modest, as in most genetic associ-ation studies (Shrout & Bolger, 2002). Finally, multiplemediation based on bootstrapping is more powerfulthan traditional approaches (e.g., Sobel test; Zhaoet al., 2010).

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5-HTTLPR, was coded 0, 1, and 2 for the long=long,short=long, and short=short genotypes, respectively,whereas prosociality, negative emotionality, and daringwere entered simultaneously to evaluate their indepen-dent contribution. The number of ADHD and ODDsymptoms constituted separate dependent variables inseparate models. Because bootstrapping does not ass-ume normality (Preacher & Hayes, 2008), the dependentvariables did not require transformation. Also, the boot-strap distribution is nonsymmetrical; thus, the reportedbetas for the indirect effect, divided by the standarderror (SE), is not equivalent to the traditional t statistic.Next, given the case-control design, and to improvespecificity, we controlled ADHD diagnostic status (i.e.,ADHD vs. non-ADHD control) when predicting ODDand controlled ODD diagnostic status (i.e., ODD vs.non-ODD control) when predicting ADHD. Race-ethnicity was a covariate in all models. We first presentthe total effect of 5-HTTLPR on ADHD and ODDexcluding prosociality, negative emotionality, and dar-ing, followed by the associations of 5-HTTLPR withtemperament dimensions, ADHD, and ODD. Third,we report the direct effect of 5-HTTLPR (i.e., the effectof 5-HTTLPR with mediators included in the model) of5-HTTLPR on ADHD and ODD, concluding with theindirect effects from the bootstrapping analyses.

RESULTS

Population Stratification

Given evidence of racial-ethnic differences in allelefrequencies of 5-HTTLPR (Gelernter, Cubells, Kidd,Pakstis, & Kidd, 1999), population stratification is athreat to the internal validity of studies with multipleracial-ethnic groups. Population stratification requiresthat race-ethnicity is significantly associated with5-HTTLPR, ADHD, and ODD (Hutchison, Stallings,McGeary, & Bryan, 2004). Youth race-ethnicity was sig-nificantly related to 5-HTTLPR, v2(10)¼ 29.004, p<.01, but was not related to ADHD, v2(4)¼ 2.73,p¼ .61, or ODD, v2(4)¼ 2.53, p¼ .64. Although popu-lation stratification was not a threat in this study,race-ethnicity was controlled in all models.

Temperament as Mediators of 5-HTTLPRand ADHD

To review, we predicted that prosociality, negative emo-tionality, and daring would mediate the association of5-HTTLPR with ADHD and ODD symptoms. First,controlling for ODD (Figure 1) and excluding tempera-ment from the model, the total effect of 5-HTTLPR wasunrelated to the total number of parent-rated ADHDsymptoms (B ¼� 0.26, SE¼ 0.48, p¼ .60) and daring

(B ¼� 0.14, SE¼ 0.33, p¼ .67). The number of longalleles inversely predicted prosociality (B¼ 1.36, SE¼0.58, p¼ .02) and marginally predicted negativeemotionality (B ¼� 0.80, SE¼ 0.43, p¼ .07). Second,prosociality inversely predicted (B ¼� 0.17, SE¼ 0.06,p< .01), whereas negative emotionality positively pre-dicted the number of ADHD symptoms (B¼ 0.28,SE¼ 0.08, p< .001); daring was unrelated to ADHD(B¼ 0.08, SE¼ 0.10, p¼ .41). Third, there was no sig-nificant direct effect of 5-HTTLPR on ADHD whenprosociality, negative emotionality, and daring wereincluded (B¼ 0.21, SE¼ 0.46, p¼ .65). We calculatedthe total and specific indirect effects of 5-HTTLPR onADHD through negative emotionality, prosociality,and daring by using 1,000 bootstrap simulation samples,yielding point estimates and the 95% bias corrected andaccelerated (BCa) confidence intervals for each indirecteffect. The total indirect effect (i.e., point estimate ofthe difference between the total effect and direct effectthrough the three mediators) significantly differed fromzero (Table 2), such that prosociality and negativeemotionality, but not daring, significantly mediated theassociation of 5-HTTLPR and the total number ofADHD (Table 2).

We then reproduced the identical models justpresented but examined teacher ratings of ADHDsymptoms. First, controlling for teacher-rated ODD(Figure 2) and excluding temperament from the model,the total effect of 5-HTTLPR was unrelated to the totalnumber of teacher-rated ADHD symptoms (B¼�0.30,SE¼ 0.55, p¼ .59) and daring (B ¼� 0.18, SE¼ 0.36,p¼ .62). However, the number of long alleles inverselypredicted prosociality (B¼ 1.86, SE¼ 0.71, p¼ .01)and positively predicted negative emotionality (B¼�1.39, SE¼ 0.59, p¼ .02). Second, prosociality inver-sely predicted the number of teacher-rated ADHD

FIGURE 1 Multiple mediator model of the effect of 5-HTTLPR on

parent-reported ADHD via temperament dimensions (beta coeffi-

cients). Note: �p� .05. ��p� .01. yp� .10.

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symptoms (B¼�0.19, SE¼ 0.07, p< .01), whereas nega-tive emotionality (B¼ 0.02, SE¼ 0.08, p¼ .79) anddaring were unrelated to ADHD (B¼ 0.13, SE¼ 0.13,p¼ .31). Third, there was no significant direct effect of5-HTTLPR on ADHD when prosociality, negativeemotionality, and daring were included in the model(B¼ 0.11, SE¼ 0.56, p¼ .84). Bootstrapping analysesrevealed that prosociality significantly mediated theeffect of 5-HTTLPR on teacher-rated ADHD symptoms(after controlling for teacher-rated ODD), whereasnegative emotionality and daring did not (Table 2).

Given that inattention and hyperactivity are separ-able with respect to their association with 5-HTTLPRand temperament (Manor et al., 2001; Martel et al.,2010), we investigated whether the potential mediating

role of prosociality, negative emotionality, and daringwas sensitive when inattention and hyperactivity symp-toms were examined separately. Using the identicaldata analytic approach just described, with control ofODD and excluding the mediators from the model, 5-HTTLPR was unrelated to inattention symptoms(B¼�0.09, SE¼ 0.30, p¼ .77). The number of 5-HTTLPR long alleles inversely predicted prosociality(B¼ 1.36, SE¼ 0.58, p¼ .02), marginally predictednegative emotionality (B¼�0.80, SE¼ 0.43, p¼ .07),but was unrelated to daring (B¼�0.14, SE¼ 0.33,p¼ .67). Second, prosociality inversely predicted(B¼�0.10, SE¼ 0.04, p¼ .01) and negative emotional-ity positively predicted the number of inattention symp-toms (B¼ 0.13, SE¼ 0.05, p< .01), whereas daringwas unrelated to inattention (B¼�0.02, SE¼ 0.06,p¼ .75). Third, the direct effect of 5-HTTLPR on inat-tention when including mediators in the model wasnot significant (B¼ 0.15, SE¼ 0.30, p¼ .63). Bootstrap-ping analyses revealed the total indirect effect of5-HTTLPR on inattention did differ from zero, suchthat prosociality and negative emotionality were indi-cated to each significantly mediate the association of5-HTTLPR and inattention whereas daring did not(Table 2).

We then tested the association of 5-HTTLPR, pro-sociality, negative emotionality, and daring with thenumber of hyperactivity symptoms, again controllingfor ODD. First, the total effect of 5-HTTLPR was unre-lated to hyperactivity with the mediators excluded(B¼�0.17, SE¼ 0.25, p¼ .51). 5-HTTLPR significantlypredicted prosociality (B¼ 1.36, SE¼ 0.58, p¼ .02) andmarginally predicted negative emotionality (B¼�0.80,SE¼ 0.43, p¼ .07) but was unrelated to daring (B¼�0.14, SE¼ 0.33, p¼ .67). Specifically, the numberof long alleles inversely predicted prosociality and

TABLE 2

Mediation by Prosociality, Negative Emotionality, and Daring on

5-HTTLPR With Total ADHD Symptoms, Inattention Symptoms,

Hyperactivity Symptoms, and ODD Symptoms

95% BCa Bootstrap CI

Point Est. SE Lower Upper

Total Parent-Rated ADHD Symptoms

Prosociality �.23 .14 �.59 �.04

Negative Emotionality �.22 .14 �.62 �.02

Daring –.01 .04 –.14 .04

Total –.47 .20 –.92 –.12

Total Teacher-Rated ADHD Symptoms

Prosociality �.35 .19 �.94 �.10

Negative Emotionality �.03 .12 �.32 .18

Daring �.02 .07 �.30 .06

Total �.41 .21 �.94 �.09

Parent-Rated Inattention Symptoms

Prosociality �.13 .08 �.37 �.02

Negative Emotionality �.10 .07 �.29 �.004

Daring .003 .02 �.03 .08

Total �.24 .11 �.51 �.06

Parent-Rated Hyperactivity Symptoms

Prosociality �.10 .07 �.28 �.01

Negative Emotionality �.12 .08 �.30 �.005

Daring �.01 .04 �.11 .06

Total �.23 .11 �.46 �.04

Total Parent-Rated ODD Symptoms

Prosociality �.06 .04 �.18 �.0002

Negative Emotionality �.31 .12 �.56 �.09

Daring �.03 .04 �.12 .05

Total �.40 .14 �.70 �.15

Total Teacher-Rated ODD Symptoms

Prosociality �.01 .05 �.14 .07

Negative Emotionality �.18 .09 �.44 �.04

Daring �.02 .05 �.16 .06

Total �.21 .11 �.50 �.04

Note: Models predicting attention-deficit=hyperactivity disorder

(ADHD) controlled for ODD diagnostic status whereas models pre-

dicting oppositional defiant disorder (ODD) controlled for ADHD

diagnostic status. All models controlled for race-ethnicity. BCa boot-

strap CI¼bias corrected and accelerated confidence intervals; Point

est.¼point estimate of the indirect effect. Boldface indicates significant

mediation.

FIGURE 2 Multiple mediator model of the effect of 5-HTTLPR on

teacher-reported ADHD via temperament dimensions (beta coeffi-

cients). Note: �p� .05. ��p� .01.

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positively predicted negative emotionality. Second,whereas prosociality was inversely related to hyper-activity (B¼�0.07, SE¼ 0.03, p¼ .02), negativeemotionality and daring were each positively associatedwith hyperactivity (B¼ 0.15, SE¼ 0.04, p< .001 andB¼ 0.10, SE¼ 0.05, p< .05, respectively). Third, thedirect effect of 5-HTTLPR on hyperactivity with media-tors included in the model was not significant (B¼ 0.07,SE¼ 0.24, p¼ .78). Bootstrapping analyses revealed thepoint estimate of total indirect effect of 5-HTTLPR onhyperactivity differed significantly from zero. Prosocia-lity and negative emotionality, but not daring, eachindependently mediated the influence of 5-HTTLPRon hyperactivity (Table 2).

We also tested how temperament mediated theeffect of 5-HTTLPR with respect to separate teacherratings of inattention and hyperactivity. Results indi-cated that prosociality, but neither negative emotion-ality nor daring, significantly mediated the effect of5-HTTLPR on both teacher-rated inattention andhyperactivity. These findings converge with the modelpredicting teacher-rated ADHD but diverge fromthe two models predicting parent-rated inattentionand hyperactivity, such that these latter two modelsconcluded that prosociality in addition negativeemotionality mediated the effect of 5-HTTLPR oninattention and hyperactivity. The results of theseanalyses are available upon request.

Temperament Mediators of 5-HTTLPR and ODD

To address the specificity of prosociality, negativeemotionality, and daring as mediators of 5-HTTLPRand parent ratings of ODD, we used the same dataanalytic approach just described (Figure 3). First,controlling for ADHD and excluding the temperament

dimensions, 5-HTTLPR was significantly related to thenumber of parent-rated ODD symptoms (B¼�0.45,SE¼ 0.21, p¼ .03). The number of long alleles againinversely predicted prosociality (B¼ 1.67, SE¼ 0.58,p< .01) and positively predicted negative emotionality(B¼�1.37, SE¼ 0.51, p< .01) but was unrelated todaring (B¼�0.24, SE¼ 0.34, p¼ .48). Second, bothnegative emotionality (B¼ 0.23, SE¼ 0.02, p< .0001)and daring (B¼ 0.11, SE¼ 0.04, p< .01) significantlypredicted the number of ODD symptoms, whereasprosociality marginally inversely predicted ODD(B¼�0.03, SE¼ 0.02, p¼ .10). Third, there was nodirect effect of 5-HTTLPR on ODD with temperamentfacets included (B¼�0.06, SE¼ 0.17, p¼ .73). Last,bootstrapping analyses estimated that the total indirecteffect of 5-HTTLPR on ODD was significantlymediated by prosociality and negative emotionality butnot daring (Table 2).

Finally, controlling for teacher-rated ADHD, usingthe previous data analytic approach, and excluding themediators from the model (Figure 4), 5-HTTLPR wasunrelated to teacher-rated ODD symptoms (B¼�0.04,SE¼ 0.22, p¼ .87). The number of 5-HTTLPR longalleles inversely predicted prosociality (B¼ 1.85,SE¼ 0.69, p< .01) and positively predicted negativeemotionality (B¼�1.43, SE¼ 0.62, p¼ .02), but it wasunrelated to daring (B¼�0.20, SE¼ 0.37, p¼ .59).Second, negatively emotionality (B¼ 0.12, SE¼ 0.03,p< .001) and daring (B¼ 0.12, SE¼ 0.05, p¼ .01), butnot prosociality (B¼�0.01, SE¼ 0.03, p¼ .84), posi-tively predicted the number of teacher-rated ODDsymptoms. Third, there was no significant direct effectof 5-HTTLPR on ODD with inclusion of the mediators(B¼ 0.17, SE¼ 0.21, p¼ .42). Bootstrapping analysesindicated that negative emotionality, but not prosociality

FIGURE 3 Multiple mediator model of the effect of 5-HTTLPR on

parent-reported ODD via temperament dimensions (beta coefficients).

Note: �p� .05. ��p� .01. yp� .10.

FIGURE 4 Multiple mediator model of the effect of 5-HTTLPR on

teacher-reported ODD via temperament dimensions (beta coefficients).

Note: �p� .05. ��p� .01.

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and daring, significantly mediated the prediction ofteacher-reported ODD symptoms from 5-HTTLPR(Table 2).

DISCUSSION

There is limited knowledge about the factors throughwhich genetic variation contributes to childhoodADHD and ODD. We evaluated prosociality, negativeemotionality, and daring as mediators of the associationof 5-HTTLPR with separate parent and teacher ratingsof ADHD and ODD using bootstrapping procedureswithin a multiple mediation framework. Among 6- to9-year-old children with and without ADHD, the num-ber of long alleles of 5-HTTLPR inversely predictedprosociality and positively predicted negative emotion-ality, but it was unrelated to daring. Controlling forODD, prosociality inversely predicted whereas negativeemotionality positively predicted parent-reportedADHD symptoms and separate counts of inattentionand hyperactivity symptoms; daring positively predictedhyperactivity but not inattention. Prosociality inverselypredicted teacher reports of ADHD symptoms, whereasnegative emotionality and daring did not. Second, con-trolling for ADHD, negative emotionality and daringeach positively predicted parent and teacher reportsof ODD symptoms whereas prosociality marginallyinversely predicted parent-reported ODD symptoms.5-HTTLPR was not significantly associated withADHD and ODD, which is consistent with expectationsof an endophenotype model. Finally, prosociality andnegative emotionality significantly mediated the asso-ciation of 5-HTTLPR with parent ratings of ADHD(controlling for ODD) and with ODD (controlling forADHD). In addition, prosociality significantly mediatedthe association of 5-HTTLPR with teacher ratings ofADHD (controlling for ODD), whereas negativeemotionality significantly mediated the association of5-HTTLPR with teacher ratings of ODD (controllingfor ADHD). These findings suggest that individual dif-ferences in prosociality and negative emotionality areimportant pathways from 5-HTTLPR to individual dif-ferences in ADHD and ODD. Moreover, both parentsand teachers agree in reporting prosociality and negativeemotionality as significant mediators of the effect of5-HTTLPR on ADHD and ODD, respectively. Thesefindings are also noteworthy given that the temperamentitems did not contain language with obvious overlapwith ADHD and ODD.

Perhaps reflecting the highly dispersed neurobiologi-cal sequelae associated with 5-HTTLPR variation,including elevated amygdala activation, 5-HTTLPRalso has pleiotropic effects across many forms of psy-chopathology (e.g., depression, anxiety; H. Clarke,Flint, Attwood, & Munafo, 2010; Munafo et al., 2008;

Munafo et al., 2009). However, the association of 5-HTTLPR with multiple dimensions of psychopathologymay be anchored in several shared endophenotypes,including temperament. Prosociality and negativeemotionality each predicted impulsivity and conductproblems in an ethnically diverse sample of adolescents,even after controlling for baseline levels (Trentacostaet al., 2009). Temperament dimensions, then, mayrepresent one nonspecific pathway from an underlyingcommon genetic predisposition to ultimate youthexternalizing behavior. Given the pleiotropic effectsassociated with 5-HTTLPR variation, future researchshould explore whether prosociality, negative emotion-ality, and daring similarly mediate pathways from5-HTTLPR to other clinical outcomes across bothexternalizing and internalizing domains (e.g., depression,anxiety), including their comorbidity.

Although there is replicated evidence that the shortallele of 5-HTTLPR affects certain dimensions oftemperament (e.g., prosociality, negative and positiveemotionality; Gyurak et al., 2013; Hayden et al., 2010),the 5-HTTLPR long allele has also been associated withADHD and ODD (Gizer et al., 2009; Nobile et al.,2007). Despite the reliable association of temperamentwith ADHD and ODD (Healey et al., 2011; Laheyet al., 2008), it is unclear which 5-HTTLPR allelescontribute to their development. One possible expla-nation of the association of the short allele with tem-perament and the long allele with psychopathology isallele flipping, or positive associations being foundbetween opposite alleles (e.g., short and long alleles of5-HTTLPR; G. M. Clarke & Cardon, 2010). Alleleflipping is increasingly common, leading to investigativeefforts to assess which allele is genuinely related todisorders of interest (G. M. Clarke & Cardon, 2010).Another rationale for inconsistent associations of thelong versus short allele is the contribution of unmea-sured environmental variation that may moderategenetic influences on psychopathology. Differentialsusceptibility contends that some genetic factorsenhance sensitivity to both environmental adversityand enrichment simultaneously, and thus the genotypesthat confer plasticity to both positive and negative envir-onments might play a role in the discrepant findings ofthe long and short alleles with phenotypes (Belskyet al., 2007). As such, although these results supportfor the role of the long allele of 5-HTTLPR in relationto ADHD and ODD, additional research is needed toclarify the functional consequences of 5-HTTLPR vari-ation. For example, variation in 5-HTTLPR is known toaffect the structure, function, and connectivity of neuralstructures and circuitry affecting negative emotion (e.g.,amygdala, perigenual cingulate; Pezawas et al., 2005).Further, the connectivity of this neural circuit wasassociated with temperamental anxiety (Pezawas et al.,

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2005), suggesting that 5-HTTLPR may affect tempera-ment through the neural circuitry thought to underlieemotion regulation. Other environmental factors thatinfluence the pathway from 5-HTTLPR to ADHD and=or ODD through temperament should also be investi-gated. For example, it is plausible that other environmen-tal conditions (e.g., parental psychopathology, parentingbehavior) might interact with 5-HTTLPR in differen-tiating whether certain youth develop ADHD and=orODD. Accordingly, exploring these moderators couldfacilitate the identification of more specific independentpathways from 5-HTTLPR to ADHD versus ODD.

This study also suggests that prosociality andnegative emotionality are potentially important influ-ences on ADHD and ODD. Given that temperamentis generally stable, reliably measured, and evident earlyin development, these findings suggest that temperamentmay usefully facilitate early identification to interruptpathways to negative outcomes and to promote positiveoutcomes (Kelvin et al., 1996; Lahey et al., 2010).Specifically, to foster resilience, early assessment ofprosociality and negative emotionality may be used totailor interventions to children. For example, parentingpractices (i.e., limit-setting, involvement) inverselypredicted child conduct problems only for youth withcertain temperament dimensions (i.e., highly resistantto control), controlling for baseline conduct problems,parenting behaviors, gender, and ethnicity (Goodnight,Bates, Pettit, & Dodge, 2008). In a randomized trial,temperament (e.g., activity=flexibility, and mood=sociability) moderated response to psychosocialinterventions for adolescent substance use disorders(Kaminer & Burleson, 2008). Thus, further researchshould identify whether prosociality and negativeemotionality moderate the efficacy of available interven-tions for children with ADHD and ODD to optimizetailored treatments.

Several study limitations should be considered whenappraising these findings. First, these are cross-sectionaldata, which prevents temporal ordering of predictors,mediators, and outcomes, a requirement for inferencesof causal mediation (Kraemer, Stice, Kazdin, Offord, &Kupfer, 2001). However, given the scarcity of mediationalmodels in psychiatric genetics and because 5-HTTLPRclearly precedes the development of temperament,ADHD, and ODD, we contend that these preliminaryresults are temporally sequenced. Future investigationsshould utilize prospective longitudinal designs to morerobustly delineate the timing of key constructs (Maxwell& Cole, 2007). Second, 5-HTTLPR effects in this studyassumed linear effects, although alternative models oftransmission should be evaluated directly (e.g., heterosis).Third, given that rs25531 was not genotyped in this study,we cannot be certain of the functionality of the long allele(Greenberg et al., 1999; Nobile et al., 1999).

The current study utilized multiple mediation toevaluate whether individual differences in temperamentdimensions significantly mediated predictions of parentand teacher ratings of ADHD and ODD from 5-HTTLPR. Prosociality and negative emotionalityemerged as important endophenotypes from 5-HTTLPRin the development of ADHD and ODD. Specifically, thenumber of long alleles was consistently inversely asso-ciated with prosociality and positively associated withnegative emotionality; in turn, prosociality was inverselyassociated with whereas negative emotionality waspositively associated with parent and teacher ratings ofADHD and ODD, respectively. Moreover, childhoodprosociality and negative emotionality mediated trajec-tories from 5-HTTLPR to parent-reported ADHD(controlling for ODD) and ODD (controlling forADHD), whereas prosociality and negative emotionalitymediated the effect of 5-HTTLPR on teacher-reportedADHDandODD,respectively.Wecontend thatgeneticallyinformative and developmentally sensitive designs (e.g.,prospective longitudinal) will provide considerabletraction on the roles of other potential endophenotypes(e.g., neural phenotypes) underlying the association ofgenetic variation and individual differences in childpsychopathology.

REFERENCES

Angold, A., Costello, E. J., & Erkanli, A. (1999). Comorbidity. Journal

of Child Psychology and Psychiatry, 40, 57–88. doi:10.1111=

1469-7610.00424

Auerbach, J., Geller, V., Lezer, S., Shinwell, E., Belmaker, R. H.,

Levine, J., & Ebstein, R. (1999). Dopamine D4 receptor (D4DR)

and serotonin transporter promoter (5-HTTLPR) polymorphisms

in the determination of temperament in 2-month-old infants.

Molecular Psychiatry, 4, 369–373. doi:10.1038=sj.mp.4000531

Baron, R. M., & Kenny, D. A. (1986). The moderator-mediator

variable distinction in social psychological research: Conceptual,

strategic, and statistical considerations. Journal of Personality and

Social Psychology, 51, 1173–1182. doi:10.1037=0022-3514.51.6.1173

Bates, J. E., Pettit, G. S., Dodge, K. A., & Ridge, B. (1998). Interaction

of temperamental resistance to control and restrictive parenting

in the development of externalizing behavior. Developmental

Psychology, 34, 982–995. doi:10.1037=0012-1649.34.5.982

Belsky, J., Bakermans-Kranenburg, M. J., & van IJzendoorn, M. H.

(2007). For better and for worse: Differential susceptibility to

environmental influences. Current Directions in Psychological

Science, 16, 300–304.

Burt, S. A. (2009). Rethinking environmental contributions to child

and adolescent psychopathology: A meta-analysis of shared environ-

mental influences. Psychological Bulletin, 135, 608–637. doi:10.1037=

a0015702

Clarke, G. M., & Cardon, L. R. (2010). Aspects of observing and

claiming allele flips in association studies. Genetic Epidemiology,

34, 266–274. doi:10.1002=gepi.20458

Clarke, H., Flint, J., Attwood, A. S., & Munafo, M. R. (2010). Asso-

ciation of the 5- HTTLPR genotype and unipolar depression:

A meta-analysis. Psychological Medicine, 40, 1767–1778. doi:10.1017=

S0033291710000516

PROSOCIALITY AND NEGATIVE EMOTIONALITY 817

Dow

nloa

ded

by [

Uni

vers

ity o

f C

ambr

idge

] at

05:

55 1

1 N

ovem

ber

2014

Collins, L. M., Graham, J. J., & Flaherty, B. P. (1998). An alternative

framework for defining mediation. Multivariate Behavioral

Research, 33, 295–312. doi:10.1207=s15327906mbr3302_5

Deault, L. C. (2010). A systematic review of parenting in relation to

the development of comorbidities and functional impairments

in children with attention-deficit=hyperactivity disorder (ADHD).

Child Psychiatry and Human Development, 41, 168–192. doi:

10.1007=s10578-009-0159-4

Dodge, K. A., & Frame, C. L. (1982). Social cognitive biases and

deficits in aggressive boys. Child Development, 53, 620–635.

doi:10.2307=1129373

Doyle, A. E., Faraone, S. V., Seidman, L. J., Willcutt, E. G., Nigg,

J. T., Waldman, I. D., Pennington, B. F., . . . Biederman, J.

(2005). Are endophenotypes based on measures of executive

functions useful for molecular genetic studies of ADHD? Journal

of Child Psychology and Psychiatry, and Allied Disciplines, 46,

774–803. doi:10.1111=j.1469-7610.2005.01476.x

Eaves, L., Rutter, M., Silberg, J. L., Shillady, L., Maes, H., & Pickles,

A. (2000). Genetic and environmental causes of covariation in

interview assessments of disruptive behavior in child and adole-

scent twins. Behavior Genetics, 30, 321–334. doi:10.1023=

A:1026553518272

Faraone, S. V., Perlis, R. H., Doyle, A. E., Smoller, J. W., Goralnick,

J. J., Holmgren, M. A., & Sklar, P. (2005). Molecular genetics of

attention-deficit=hyperactivity disorder. Biological Psychiatry, 57,

1313–1323. doi:10.1016=j.biopsych.2004.11.024

Fergusson, D. M., & Horwood, L. J. (1995). Predictive validity of

categorically and dimensionally scored measures of childhood

behaviors. Journal of the American Academy of Child & Adolescent

Psychiatry, 34, 477–485. doi:10.1097=00004583-199504000-00015

Froehlich, T. E., Lanphea, B. P., Epstein, J. N., Barbaresi, W. J.,

Katusic, S. K., & Kahn, R. S. (2007). Prevalence, recognition, and

treatment of attention-deficity=hyperactivity disorder in a national

sample of US children. Archives of Pediatrics & Adolescent Medicine,

161, 857–864. doi:10.1001=archpedi.161.9.857

Gelernter, J., Cubells, J., Kidd, J., Pakstis, A., & Kidd, K. (1999).

Population studies of polymorphisms of the serotonin transporter

protein gene. American Journal of Medical Genetics - Neuropsy-

chiatric Genetics, 88, 61–66. doi:10.1002=(SICI)1096-

8628(19990205)88:1<61::AID-AJMG11>3.0.CO;2-K

Gizer, I. R., Ficks, C., & Waldman, I. D. (2009). Candidate gene

studies of ADHD: A meta-analytic review. Human Genetics, 126,

51–59. doi:10.1007=s00439-009-0694-x

Glenn, A. L., Raine, A., Venables, P. H., & Mednick, S. A. (2007).

Early temperamental and psychophysiological precursors of adult

psychopathic personality. Journal of Abnormal Psychology, 116,

508–518. doi:10.1037=0021-843X.116.3.508

Goodnight, J. A., Bates, J. E., Pettit, G. S., & Dodge, K. A. (2008).

Parents’ campaigns to reduce their children’s conduct problems:

Interactions with temperamental resistance to control. European

Journal of Developmental Science, 2, 100–119.

Gottesman, I. I., & Gould, T. D. (2003). The endophenotype concept

in psychiatry: Etymology and strategic intentions. The American

Journal of Psychiatry, 160, 636–645. doi:10.1176=appi.ajp.160.4.636

Greenberg, B. D., Tolliver, T. J., Huang, S. J., Li, Q., Bengel, D., &

Murphy, D. L. (1999). Genetic variation in the serotonin transporter

promoter region affects serotonin uptake in human blood platelets.

American Journal of Medical Genetics, 88, 83–87.

Greene, R. W., Biederman, J., Zerwas, S., Monuteaux, M. C., Goring,

J. C., & Faraone, S. V. (2002). Psychiatric comorbidity, family dys-

function, and social impairment in referred youth with oppositional

defiance disorder. American Journal of Psychiatry, 159, 1214–1224.

doi:10.1176=appi.ajp.159.7.1214

Gyurak, A., Haase, C. M., Sze, J., Goodkind, M. S., Coppola, G.,

Lane, J., Miller, B. L., . . . Levenson, R. W. (2013). The effect of

the serotonin transporter polymorphism (5-HTTLPR) on empathic

and self-conscious emotional reactivity. Emotion, 13, 25–35.

doi:10.1037=a0029616

Hariri, A. R., Mattay, V. S., Tessitore, A., Kolachana, B., Fera, F.,

Goldman, D., . . . Weinberger, D. R. (2002). Serotonin transporter

genetic variation and the response of the human amygdala. Science,

297, 400–403. doi:10.1126=science.1071829

Hayden, E. P., Klein, D. N., Sheikh, H. I., Olino, T. M., Dougherty, L.

R., Dyson, M. W., . . . Singh, S. M. (2010). The serotonin trans-

porter promoter polymorphism and childhood positive and negative

emotionality. Emotion, 10, 696–702. doi:10.1037=a0019527

Healey, D. M., Marks, D. J., & Halperin, J. M. (2011). Examining the

interplay among negative emotionality, cognitive functioning, and

attention deficit=hyperactivity disorder symptom severity. Journal

of the International Neuropsychological Society, Apr 5, 1–9.

doi:10.1017=S1355617711000294

Heils, A., Teufel, A., Petri, S., Stober, G., Riederer, P., Bengel, D., &

Lesch, K. P. (1996). Allelic variation of human serotonin transporter

gene expression. Journal of Neurochemistry, 66, 2621–2624.

doi:10.1046=j.1471-4159.1996.66062621.x

Hinshaw, S. P. (1987). On the distinction between attentional deficits=

hyperactivity and conduct problems=aggression in child psycho-

pathology. Psychological Bulletin, 101, 443–463. doi:10.1037=0033-

2909.101.3.443

Holmes, A, Murphy, D. L., & Crawley, J. N. (2002). Reduced

aggression in mice lacking the 5-HT transporter. Psychopharma-

cology, 161, 160–167. doi:10.1007=s00213-002-1024-3

Holmes, A., Yang, R. J., Lesch, K.-P., Crawley, J. N., & Murphy, D.

L. (2003). Mice lacking the serotonin transporter exhibit 5-HT(1A)

receptor-mediated abnormalities in tests for anxiety-like behavior.

Neuropsychopharmacology, 28, 2077–2088. doi:10.1038=sj.npp.

1300266

Hoza, B., Mrug, S., Gerdes, A. C., Hinshaw, S. P., Bukowski, W. M.,

Gold, J. A., . . . Arnold, L. E. (2005). What aspects of peer relation-

ships are impaired in children with attention-deficit=hyperactivity

disorder? Journal of Consulting and Clinical Psychology, 73, 411–

423. doi:10.1037=0022-006X.73.3.411

Hutchison, K. E., Stallings, M., McGeary, J., & Bryan, A. (2004).

Population stratification in the candidate gene study: Fatal threat

or red herring? Psychological Bulletin, 130, 66–79. doi:10.1037=

0033-2909.130.1.66

Kaminer, Y., & Burleson, J. A. (2008). Does temperament moderate

treatment response in adolescent substance use disorders? Substance

Abuse: Official Publication of the Association for Medical Education

and Research in Substance Abuse, 29, 89–95. doi:10.1080=

08897070802093387

Kazdin, A. E. (1995). Conduct disorders in childhood and adolescence.

Thousand Oaks, CA: Sage.

Kelvin, R., Goodyer, I., & Altham, P. (1996). Temperament and

psychopathology amongst siblings of probands with depressive

and anxiety disorders. Journal of Child Psychology and Psychiatry,

37, 543–550. doi:10.1111=j.1469-7610.1996.tb01440.x

Kent, K. M., Pelham, W. E., Jr., Molina, B. S. G., Sibley, M. H.,

Waschbusch, D. A., Yu, J., . . . Karch, K. M. (2011). The academic

experience of male high school students with ADHD. Journal of

Abnormal Child Psychology, 39, 451–462. doi:10.1007=s10802-

010-9472-4

Kraemer, H. C., Stice, E., Kazdin, A., Offord, D., & Kupfer, D.

(2001). How do risk factors work together? Mediators, moderators,

and independent, overlapping, and proxy risk factors. Americal

Journal of Psychiatry, 158, 848–856. doi:10.1176=appi.ajp.158.6.848

Lahey, B., Applegate, B., McBurnett, K., Biederman, J., Greenhill, L.,

Hynd, G., . . . Richters, J. (1994). DSM-IV field trials for attention

deficit hyperactivity disorder in children and adolescents. American

Journal of Psychiatry, 151, 1673–1685.

818 BRAMMER AND LEE

Dow

nloa

ded

by [

Uni

vers

ity o

f C

ambr

idge

] at

05:

55 1

1 N

ovem

ber

2014

Lahey, B. B., Applegate, D., Chronis, A. M., Jones, H. A., Williams,

S. H., Loney, J., & Waldman, I. D. (2008). Psychometric charac-

teristics of a measure of emotional dispositions developed to test

a developmental propensity model of conduct disorder. Journal of

Child Clinical and Adolescent Psychology, 37, 794–807. doi:10.1080=

15374410802359635

Lahey, B. B., Pelham, W. E., Loney, J., Kipp, H., Ehrhardt, A., Lee, S.

S., et al. (2004). Three-year predictive validity of DSM-IV attention-

deficit=hyperactivity disorder in children diagnosed at 4–6 years of

age. American Journal of Psychiatry, 161, 2014–2020.

Lahey, B. B., Rathouz, P. J., Applegate, B., Tackett, J. L., &

Waldman, I. D. (2010). Psychometrics of a self-report version of

the Child and Adolescent Dispositions Scale. Journal of Clinical

Child and Adolescent Psychology, 39, 351–361. doi:10.1080=

15374411003691784

Lee, S. S., Lahey, B. B., Owens, E. B., & Hinshaw, S. P. (2008). Few

preschool boys and girls with ADHD are well-adjusted during

adolescence. Journal of Abnormal Child Psychology, 36, 373–383.

doi:10.1080=15374410802575313

Lynn, D. E., Lubke, G., Yang, M., McCracken, J. T., McGough, J. J.,

Ishii, J., . . . Smalley, S. L. (2005). Temperament and character

profiles and the dopamine D4 receptor gene in ADHD. American

Journal of Psychiatry, 162, 906–913. doi:10.1176=appi.ajp.162.5.906

MacKinnon, D. P., Krull, J. L., & Lockwood, C. M. (2000).

Equivalence of the mediation, confounding and suppression effect.

Prevention Science: The Official Journal of the Society for Prevention

Research, 1, 173. doi:10.1023=A:1026595011371

Malmberg, K., Wargelius, H. L., Lichtenstein, P., Oreland, L., &

Larsson, J. O. (2008). ADHD and disruptive behavior scores:

Associations with MAO-A and 5-HTT genes and with platelet

MAO-B activity in adolescents. BMC Psychiatry, 8, 28–36.

doi:10.1186=1471-244X-8-28

Manor, I., Eisenberg, J., Tyano, S., Sever, Y., Cohen, H., Ebstein, R.

P., & Kotler, M. (2001). Family-based association study of the

serotonin transporter promoter region polymorphism (5-HTTLPR)

in attention deficit hyperactivity disorder. American Journal of

Medical Genetics, 105, 91–95. doi:10.1002=1096-8628(20010108)105:

1<91::AID-AJMG1069>3.0.CO;2-V

Martel, M. M., Nikolas, M., Jernigan, K., Friderici, K., & Nigg, J. T.

(2010). Personality mediation of genetic effects on attention-deficit=

hyperactivity disorder. Journal of Abnormal Child Psychology,

38, 633–643. doi:10.1007=s10802-010-9392-3

Maxwell, S. E., & Cole, D. A. (2007). Bias in cross-sectional analyses

of longitudinal mediation. Psychological Methods, 12, 23–44.

doi:10.1037=1082-989X.12.1.23

Moffitt, T. E., Caspi, A., & Rutter, M. (2005). Strategy for

investigating interactions between measured genes and measured

environments. Archives of General Psychiatry, 62, 473–481. doi:10.1001=

archpsyc.62.5.473

Munafo, M. R., Brown, S. M., & Hariri, A. R. (2008). Serotonin

transporter (5-HTTLPR) genotype and amygdala activation:

A meta-analysis. Biological Psychiatry, 63, 852–857. doi:10.1016=

j.biopsych.2007.08.016

Munafo, M. R., Freimer, N. B., Ng, W., Ophoff, R., Veijola, J.,

Miettunen, J., . . . Flint, J. (2009). 5-HTTLPR genotype and anxiety-

related personality traits: A meta-analysis and new data. American

Journal of Medical Genetics. Part B, Neuropsychiatric Genetics:

The Official Publication of the International Society of Psychiatric

Genetics, 150B, 271–281. doi:10.1002=ajmg.b.30808

Nobile, M., Begni, B., Giorda, R., Frigerio, A., Marino, C., Molteni,

M., et al. (1999). Effects of serotonin transporter promoter genotype

on platelet serotonin transporter functionality in depressed children

and adolescents. Journal of the American Academy of Child and Ado-

lescent Psychiatry, 38, 1396–1402.

Nobile, M., Giorda, R., Marino, C., Carlet, O., Pastore, V., Vanzin,

L., . . . Battaglia, M. (2007). Socioeconomic status mediates the

genetic contribution of the dopamine receptor D4 and serotonin

transporter linked promoter region repeat polymorphisms to exter-

nalization in preadolescence. Development and Psychopathology,

19, 1147–1160. doi:10.1017=S0954579407000594

Pelham, W. E., Jr., Gnagy, E. M., Greenslade, K. E., & Milich, R.

(1992). Teacher ratings of DSM-III-R symptoms for the disruptive

behavior disorders. Journal of the American Academy of Child and

Adolescent Psychiatry, 31, 210–218.

Pezawas, L., Meyer-Lindenberg, A., Drabant, E. M., Verchinski, B.

A., Munoz, K. E., Kolachana, B. S., . . . Weinberger, D. R. (2005).

5-HTTLPR polymorphism impacts human cingulate-amygdala

interactions: A genetic susceptibility mechanism for depression.

Nature Neuroscience, 8, 828–834. doi:10.1038=nn1463

Preacher, K. J., & Hayes, A. F. (2008). Asymptotic and resampling

strategies for assessing and comparing indirect effects in multiple

mediator models. Behavior Research Methods, 40, 879–891. doi:

10.3758=BRM.40.3.879

Rhee, S. H., & Waldman, I. D. (2002). Genetic and environmental

influences on antisocial behavior: A meta-analysis of twin and adop-

tion studies. Psychological Bulletin, 128, 490–529. doi:10.1037=

0033-2909.128.3.490

Rothbart, M. K., & Derryberry, D. (1981). Development of individual

differences in temperament. In M. E. Lamb & A. L. Brown (Eds.),

Advances in developmental psychology (Vol. 1, pp. 37–86). Hillsdale,

NJ: Erlbaum.

Rowe, R., Costello, E. J., Angold, A., Copeland, W. E., & Maughan,

B. (2010). Developmental pathways in oppositional defiant disorder

and conduct disorder. Journal of Abnormal Psychology, 119, 726–

738. doi:10.1037=a0020798

Rutter, M. (2006). Genes and behavior: Nature–nurture interplay

explained. Oxford: Blackwell.

Sakai, J. T., Young, S. E., Stallings, M. C., Timberlake, D., Smolen,

A., Stetler, G. L., & Crowley, T. J. (2006). Case-control and within-

family tests for an association between conduct disorder and

5HTTLPR. American Journal of Medical Genetics Part B: Neuropsy-

chiatric Genetics, 141B, 825–832. doi:10.1002=ajmg.b.30278

Saudino, K. J. (2005). Behavioral genetics and child temperament.

Journal of Developmental and Behavioral Pediatrics, 26, 214–223.

doi:0196-206X=05=2603- 0214

Shaffer, D., Fisher, P., Lucas, C. P., Dulcan, M. K., & Schwab-Stone,

M. E. (2000). NIMH diagnostic interview schedule for children ver-

sion IV (NIMH DISC-IV): Description, differences from previous

versions, and reliability of some common diagnoses. Journal of the

American Academy of Child and Adolescent Psychiatry, 39, 28–38.

doi:10.1097=00004583-200001000-00014

Shrout, P. E., & Bolger, N. (2002). Mediation in experimental and

nonexperimental studies: New procedures and recommendations.

Psychological Methods, 7, 422–445.

Sonuga-Barke, E. J. S., Oades, R. D., Psychogiou, L., Chen, W.,

Franke, B., Buitelaar, J., . . . Faraone, S. V. (2009). Dopamine and

serotonin transporter genotypes moderate sensitivity to maternal

expressed emotion: The case of conduct and emotional problems

in attention deficit=hyperactivity disorder. Journal of Child Psy-

chology and Psychiatry, 50, 1052–1063. doi:10.1111=j.1469-7610.

2009.02095.x

Trentacosta, C. J., Hyde, L. W., Shaw, D. S., & Cheong, J. (2009).

Adolescent dispositions for antisocial behavior in context: The roles

of neighborhood dangerousness and parental knowledge. Journal of

Abnormal Psychology, 118, 564–575. doi:10.1037=a0016394

Zhao, X., Jr., Lynch, J. G., & Chen, Q. (2010). Reconsidering Baron

and Kenny: Myths and truths about mediation analysis. Journal of

Consumer Research, 37, 197–206. doi:10.1086=651257

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