Memory bias for health-related information in somatoform disorders

Journal of Psychosomatic Res

Memory bias for health-related information in somatoform disorders

Alexandra Martin4, Anika Buech, Christina Schwenk, Winfried Rief

Section for Clinical Psychology and Psychotherapy, Philipps-University Marburg, Marburg, Germany

Received 1 June 2006; received in revised form 3 April 2007; accepted 1 May 2007

Abstract

Objective: Cognitive processes are considered to be relevant to

the etiology and maintenance of somatoform disorders (SFDs). The

aim of this study was to assess explicit and implicit information-

processing bias for disorder-congruent information in SFDs.

Methods: A clinical sample of 33 patients suffering from multiple

somatoform symptoms (SSI-3/5) and 25 healthy controls per-

formed an encoding task with computer-presented word lists

(illness related, negative, positive, neutral content), subsequently

0022-3999/07/$ – see front matter D 2007 Elsevier Inc. All rights reserved.

doi:10.1016/j.jpsychores.2007.05.005

4 Corresponding author. Section for Clinical Psychology and Psycho-

therapy, Philipps-University, Gutenbergstr. 18, D-35032 Marburg,

Germany. Tel.: +49 6421 282 3656, +49 6421 282 3657; fax: +49 6421

2828904.

E-mail address: [email protected] (A. Martin).

followed by explicit memory tests (free recall and recognition) and

an implicit test (word-stem completion). Results: The somatoform

group showed a memory bias for illness-related stimuli in the

word-stem completion task, whereas the two groups did not differ

in explicit memory tests. This effect could not be explained by

comorbid depression. Conclusion: These results provide some

support for current theories on SFDs.

D 2007 Elsevier Inc. All rights reserved.

Keywords: Information-processing bias; Cognitive model; Memory; Somatoform disorder; Somatization

Introduction

Somatoform disorders (SFDs), according to the Diag-

nostic and Statistical Manual of Mental Disorders, Fourth

Edition, Text Revision (DSM-IV-TR) and the International

Classification of Diseases, Tenth Revision (ICD-10), cover

a heterogeneous range of conditions, all of them sharing

the central feature of bodily symptoms that cannot be

fully explained by any medical factor. The impact of

SFDs on the health care system is tremendous, as SFDs

are among the most prevalent psychiatric disorders and,

moreover, are associated with severe impairment in

important areas of functioning and with high health care

utilization [1–4].

In current models of SFDs, information-processing

aspects are considered to be relevant [5–8]. These include

an abnormal amplifying perceptual style [5], restrictive

assumptions about health and body functions [9], and an

enduring tendency to misinterpret bodily sensations and

other health-related information as evidence of serious

physical illness [10]. The interaction of perceptual and

interpretative biases of ambiguous body signals can result

in a vicious circle of anxiety, physiological arousal, and

intensification of symptoms (Fig. 1). Furthermore, organic

causal beliefs and vulnerability attributions have been

found to be associated with dysfunctional illness behavior

[11], which in turn might contribute to the process of the

syndrome becoming chronic.

In cognitive–behavioral theories of SFDs, it has been

outlined that beliefs about physical sensations signaling

serious illnesses increase anxiety concerning health, which

can then lead to selective cognitive biases favoring

information that confirms illness belief while discounting

information that contradicts it. Cognitive biases can occur

at different stages of information processing, either at the

encoding-of-information stage, indicated by an attentional

(or preattentional) bias for disorder-relevant stimuli

(bintegrative processQ), or at the point of volitional

retrieval of information from memory, indicating deeper

elaboration of schema-congruent information (belaboration

earch 63 (2007) 663–671

Fig. 1. The cognitive–psychobiological model of SFDs (modified from Rief

and Nanke [6]).

A. Martin et al. / Journal of Psychosomatic Research 63 (2007) 663–671664

processQ). Aspects of information processing have also

contributed to the understanding of mood and anxiety

disorders. Williams et al. [12,13] provided a cognitive

model of information processing in order to account for

different mnemonic and attentional biases found in these

disorders (e.g., Refs. [14–16]). According to Williams et

al., anxiety is associated with automatic encoding of

fearful stimuli, whereas depression is more likely asso-

ciated with elaboration of negative emotional stimuli.

Accordingly, the bias occurring at integration stage can be

revealed by implicit tests such as perception-based or

word-stem completion tasks, whereas biases related to

elaboration stages of information processing can be

revealed by explicit memory tests (e.g., free recall or

recognition of previously learned material).

The influence of memory in SFDs has been inves-

tigated in a few studies only, with most of them studying

explicit memory effects. In regard to chronic pain

disorders, a couple of findings suggest a memory bias

for pain-related information (sensory words) [17]. How-

ever, these findings should be generalized to SFDs with

caution, as many of the studies investigated chronic pain

conditions with some kind of pathophysiological findings

(e.g., arthritis), and information processes might differ

from SFDs. Results from studies regarding hypochondria-

sis are mixed. Durso et al. [18] could not demonstrate

biases for health-related information with a recognition

task in hypochondriac students. However, in a study by

Brown et al. [19], hypochondriacal individuals did not

show a perceptual bias for health-related information but

did, however, demonstrate evidence suggesting a memory

bias: Within-group comparisons showed that two hypo-

chondriacal samples recalled more health-related words

than nonhealth words, whereas the effects in control

samples were not significant. Pauli and Alpers [20]

reported that patients with hypochondriasis and somato-

form pain disorder and patients with hypochondriasis

without pain disorder showed an enhanced immediate

recall of pain-related words.

Only very few studies assessed memory bias in subjects

suffering from multiple somatoform symptoms, such as in

somatization disorder or undifferentiated SFDs. Rief et al.

[21], using a word category decision task and subsequent free

recall, did not demonstrate a disorder-specific explicit

memory bias in these subjects. Scholz et al. [22] also did

not find an explicit information-processing bias based on an

auditorily presented lexical decision task in students with

multiple somatoform symptoms. However, their results

suggested an implicit information-processing bias for threat-

ening health-related words. In a recent study, a group of SFD

patients showed an explicit memory bias for physical threat

words (the free-recall ratio of physical threat words was

higher than that in controls), as well as supraliminal inter-

ferences for physical threat words in the emotional Stroop

task; the study did not, however, reveal an implicit memory

bias in the tachistoscopic word-identification task [23].

Overall, the number of experimental studies on

information-processing bias in SFDs, especially in soma-

tization disorders or related groups with multiple somato-

form symptoms, is still very limited, and existing studies

have focused mainly on elaborative processes, revealing

inconsistent results. Therefore, the aim of the present

study was to assess memory biases for disorder-congruent

stimuli in SFDs. A clinical sample of patients suffering

from multiple somatoform symptoms and healthy controls

performed an encoding task with computer-presented word

lists (illness related, negative, positive, neutral content),

subsequently followed by standard explicit memory tests

(free recall, recognition) and an implicit test (a word-stem

completion task). We hypothesized that individuals with

multiple somatoform symptoms would show a memory

bias favoring health-related information in explicit and

implicit tasks. As comorbidity with depression is high in

SFDs, we additionally controlled for its influence in

secondary analyses.

Method

Sample

Somatization syndrome group

Subjects were included in the clinical sample only if

multiple somatoform symptoms were present as per the

criterion of the bsomatization indexQ (SSI-3/5), which was

assessed with Screening for Somatoform Symptoms 2

(SOMS-2). According to this criterion, men had to report

at least three somatoform symptoms and women had to

report at least five somatoform symptoms as being present

during the past 2 years (SOMS-2) and which could not be

explained by medical/organic factors. The SSI-3/5 criterion

corresponds to Escobar et al.’s SSI-4/6 proposal to classify

somatization syndrome [24].

Control group

Healthy controls did not fulfill the SSI-3/5 criterion for

somatization syndrome. If any symptoms were reported

A. Martin et al. / Journal of Psychosomatic Research 63 (2007) 663–671 665

(SOMS-2), they needed to be rated as being medically

explained by their physicians (SOMS-2 Item 55: yes,

reported symptoms could be explained with a medical

explanation by their physician).

The total sample comprised 58 subjects: 33 in the

somatoform group (SFDs) and 25 in the healthy control

group. The majority of subjects of the study’s clinical

sample were patients with SFDs who contacted the Depart-

ment of Clinical Psychology and Psychotherapy and the

outpatient clinic for various reasons (n=23). Participants of

the somatization syndrome group were recruited with an

advertisement in local papers (n=10). The control group

comprised volunteers who were recruited mainly by means

of an advertisement requesting for volunteers for a

psychological experiment.

Assessment/questionnaires

SOMS-2 [24,25] is a self-report instrument for the

detection of SFDs that was used as the measure of

somatization syndrome (yes/no) in the present study. It lists

53 bodily symptoms covering all somatoform symptoms

mentioned in DSM-IV-TR and ICD-10 as occurring in

somatization disorders. Subjects were asked to indicate the

symptoms that were present during the past 2 years and for

which physicians had not been able to find a clear organic

cause. An additional 15 items directly refer to classification

criteria, such as disability due to symptoms, frequent doctor

visits, onset, and duration. Item 55 asks for a confirmation

that the previously indicated symptoms could not be

explained by any known medical condition. The psycho-

metric properties of SOMS-2 are well established, with

good test–retest reliability (72 h; r=. 85), high internal

consistency (.88), high discriminant validity, high sensitivity

(98%), and acceptable specificity (63%), to correctly

identify patients with a clinically relevant somatization

syndrome (as defined by the somatization syndrome SSI-4/6

of Escobar et al. [26]). Correlations between SOMS and

structured clinical interviews varied between .72 and .82 for

various somatization indices.

The state version of Screening for Somatoform Symp-

toms 7 (SOMS-7) was used to identify the number and the

severity of somatoform symptoms that subjects suffered

from during the last 7 days. The scale has shown a high

internal consistency (a=.92) and sensitivity to change

following treatment [27]. The mean severity score varies

between 0 and 4 (only symptoms of at least moderate

disability were counted for the current symptom number).

The Whitely Index (WI) [28,29] is a self-report

questionnaire widely used for assessing degrees of hypo-

chondriac anxiety and concern, with excellent reliability and

validity [30,31]. The 14-item version with dichotomous

response alternatives was used, with the total score varying

between 0 and 14.

The Beck Depression Inventory (BDI) [32,33] was used

as a measure to assess the severity of depressive symptoms.

While its psychometric properties have not yet been

established explicitly in SFDs, a range of studies have

shown high internal consistencies (mean a=.87) and

moderate to high concurrent validities (r’sz.6–.76) of the

BDI in psychiatric and nonpsychiatric samples (e.g.,

medical and chronic pain patients) [34].

Intelligence quotient (IQ) was assessed with a vocabu-

lary test (Mehrfachwahl-Wortschatz-Intelligenztest (MWT-

B) [35]. MWT-B is an economic measure of global

crystallized intelligence. The instrument has been shown

to be valid in psychiatric populations and is recommended

for sample descriptions [36]. In the present study, it was

used to control for comparable IQ levels across the clinical

and control groups.

Materials

Four types of word stimuli were used in the memory

tasks: two types of emotionally negative words [illness

related (e.g., breathlessness, infection, stroke) and general

negative words (e.g., failure, jealousy, war)], emotionally

positive words (e.g., affection, confidence, compliment),

and neutral words (e.g., ballpen, carpet, paper). Construc-

tion of the word list material was based on word stimuli

previously used in comparable experiments [20,22,37],

self-report questionnaires [38,39], and expert inputs,

resulting in a primary word list of 200 words, with 50

words in each word category. This primary word list was

presented to 50 adult students of multiple disciplines who

were asked to rate the category (illness related, emotionally

negative, emotionally positive, neutral) of each word. Only

those words for which at least 80% of the subjects rated

the correct category were considered for further inclusion.

Each illness-related word was matched with one word of

each of the other categories with respect to word length

[number of syllables (mean/S.D.): illness-related 3.00/0.67,

negative 3.00/0.67, positive 3.00/0.67, neutral 2.83/0.75]

and word frequency (illness-related 12.8/4.6, negative

12.8/5.4, positive 12.8/4.6, neutral 12.8/4.6; according to

http://wortschatz.uni-leipzig.de).

Based on these results, 48 completely parallelized

words (12 per category) were chosen for the encoding

and free-recall task (Appendix). In addition, 48 partially

parallelized words (12 per category) were selected as

unprimed material for the recognition task. The word-stem

completion task consisted of 44 of 48 words of the encoding

task (11 words per category). Three words were excluded as

their word stems did not offer an alternative word

completion with a comparable word frequency (negative:

ignorance; positive: tenderness; neutral: encyclopedia),

and one word was excluded because the word stem

could be completed by either an illness-related word or a

positive word.

In addition, the independent Student’s sample (n=50)

rated the degree of threat of all illness-related and negative

words on a 4-point scale (0=not at all, 3=very much) to

http://wortschatz.uni-leipzig.de


ensure the comparable emotional valence of these two word

types. The mean emotional valence of illness-related words

(mean=2.59, S.D.=0.44) did not differ from the mean

valence of negative words (mean=2.56, S.D.=0.43)

[t(49)=0.57, PN.05].

Procedure

Encoding and free recall

A random selection of three words from each category

was subsequently assigned to four blocks (A, B, C, D) in

random order. One additional filling word was presented at

the beginning and one additional filling word was presented

at the end of each block to avoid primacy and recency

effects; thus, the blocks comprised 14 words each. This

within-block word order was kept stable for the encoding

task. Four-word stimuli blocks were then combined into

four presentation sequences (ABCD, BCDA, CDAB,

DABC) so that each block was presented with the same

frequency at each position. Sequence presentations were

balanced across all subjects, and its possible effect was

analyzed (see Results). The words were presented in white

letters (font type: Arial; font size: 48) against a black

background on a computer screen (15 in.; flat-panel display;

1024�768-pixel resolution) positioned 70 cm in front of

seated subjects.

Each task was preceded by written instructions on the

screen, which were rephrased by the investigator. Prior to

each encoding block, the subjects were instructed to

memorize the words by relating them to subjectively

relevant events. The subjects started the presentation of

the words individually. Each word was presented for 7 s.

Each of the four encoding blocks was followed by a 3-min

distraction task (a visual search for differences between two

almost identical drawings). The first explicit memory task

(free recall) took place thereafter. During a 5-min period,

subjects were asked to write down all words they

remembered. Subjects had to complete the sequence of

bencoding–distraction task–free recallQ four times.1

Word-stem completion

The next task consisted of a word-stem completion test

(implicit memory). A list of 44 word stems (three or four

letters of encoding words in random order) was presented,

and subjects were asked to complete the letters by

choosing the first word that came into mind within a

maximum of 5 min.

1 Control for word order effects: Recall rates regarding absolute word

position in the encoding sequence differed significantly [ F(47, 2632)=2.7,

Pb .01]. Graphical control clearly demonstrated higher recall rates for the

first word of each block (one per category), suggesting a primacy effect.

When these four stimuli were eliminated from analysis, the word order

effect disappeared [ F(43, 2408)=1.33, PN.10)].

Recognition

Afterwards, a word list of 48 primed words and 48

unprimed words (24 of each word type in random order)

was presented. Subjects were instructed to indicate the

words they remembered to have been presented during the

encoding phase. Again, a maximum of 5 min was allowed to

accomplish the last explicit memory task.

Questionnaires

In order to avoid bcontaminatingQ the effects of ques-

tionnaire items, subjects filled in the questionnaire battery

(MWT-B, SOMS-2, SOMS-7, WI and BDI) after the

memory tasks.

Statistical analysis

Dependent variables

Free recall : the number of correctly recalled words per

category and block was counted for each

subject; the total number of correctly

recalled words per category was entered

for analysis.

Recognition : the variable dV (sensitivity index; derived

from signal detection analysis) was computed

from the bhit rateQ and bfalse alarm rateQvariables of each word type for each subject

(correctly identified words minus false-pos-

itive words).

Word-stem completion : the dependent variable was

derived from the number of words completed

correctly according to the priming list per

category.

Analysis

Recall data were subjected to analysis of variance, with

group as the between-subjects factor and word type as the

within-subject factor. Two (Group)�four (Word Type)

analyses of variances were conducted. In case of significant

main effects of the word type factor, planned contrasts

(Helmert) were conducted to compare the memory of

illness-related words with those of the other three categories.

In case of a significant interaction (according to our

hypotheses), subsequent multivariate analyses of variance

(MANOVA) for each group were computed to clarify the

nature of the interaction. The significance level of global

statistical tests was Pb .05 for planned contrasts according to

directed hypotheses (one tailed). All MANOVA were based

on Greenhouse–Geisser correction of degrees of freedom.

Effect sizes were computed as partial g2 values or Cohen’sd. Additional analyses of covariance (ANCOVA) were

conducted to control for the possibly confounding effect of

group differences in depression.

Post-hoc power analyses for MANOVA ( f=0.25, a=.05,N=59) revealed a power of .97 for medium between-factor

Table 1

Sociodemographic and clinical characteristics

Characteristics SFD group (n=33) Control group (n=25) Statistics

Sociodemographic

Gender (female/male) 24/9 16/9 v2(1)=0.51

Age in years [mean (S.D.)] 49.58 (10.54) 45.88 (10.2) t(56)=1.34

Education (b10 years/z10 years) 9/24 1/24 v2(1)=5.404

Employed (yes/no) 22/11 15/10 v2(1)=0.27

Intelligence (MWT-B) [mean (S.D.)] 119.52 (14.04) 124.88 (9.49) t(55)=�1.62Clinical [mean (S.D.)]

SOMS-2, somatoform symptoms, last 2 years 15.00 (6.57) 1.96 (2.11) t(56)=9.52444

SOMS-7, somatoform symptoms, last 7 days 5.36 (4.19) 0.60 (1.47) t(56)=5.43444

SOMS-7, symptom intensity, last 7 days 0.38 (0.23) 0.05 (0.10) t(56)=6.59444

WI, health anxiety, last 7 days 5.15 (3.68) 1.63 (1.76) t(56)=4.41444

BDI, depression severity, last 7 days 17.26 (14.2) 7.35 (9.06) t(55)=3.0444

4 Pb.05.

44 Pb.01.

444 Pb.001.


effects, .89 for within-factor effects, .31 for medium-

interaction effects, and .70 for large-interaction effects

( f=0.40).

Differences in sociodemographic and descriptive clinical

variables were determined using t tests, where appropriate,

and chi-square test for nominal data. All analyses were

conducted using SPSS statistical package (version 12.0;

SPSS Inc., Chicago, IL, USA).

Table 2

Results of memory tasks: number of words, by category per group

Participant group

Word type [mean (S.D.)]

Illness related Negative Positive Neutral

Free recall

SFD group (n=33) 5.97 (2.08) 4.91 (2.99) 4.42 (2.56) 5.61 (2.61)

Control group (n=25) 6.52 (2.40) 5.28 (2.09) 5.12 (2.44) 6.56 (2.82)


SFD group (n=33) 4.15 (1.97) 3.45 (1.64) 2.45 (1.25) 3.12 (1.32)

Control group (n=25) 3.16 (1.86) 3.04 (1.27) 2.44 (1.15) 3.20 (1.58)

Recognition dVSFD group (n=33) 9.97 (1.51) 8.79 (2.13) 7.82 (2.95) 9.21 (2.32)

Control group (n=25) 9.52 (1.69) 8.32 (2.51) 7.52 (2.88) 9.16 (2.14)

Results

Subject characteristics

Gender ratio and mean age were comparable between

groups (Table 1). Although the two groups differed with

respect to school education, with a higher number of control

subjects having attended school for at least 10 years, there

were no differences in current working status and mean

verbal intelligence level (MWT-B).

As expected, the SFD group showed a higher number

of lifetime and current somatoform symptoms, higher

symptom severity, more health anxiety, and higher

depression scores.

Free recall

The results of the memory tasks are shown in Table

2. The first explicit memory task consisted of free recall

of all words presented during the encoding task (primed

word list). The SFD group and the control group did

not differ in their overall recall [F(1,56)=1.51]. There

was a main effect for Word Type [F(3,168)=9.06,

Pb.001, partial g2=.14], showing that the overall free

recall of illness-related words was significantly better

than any of the other three-word categories [F(1,56)=

13.01, Pb.01, partial g2=.19]. Paired comparisons

showed higher recall rates for illness-related words than

for unspecific negative and positive words. However,

contrary to our hypotheses, the SFD group did not show

better recall of illness-related words compared to

controls; the interaction Group�Word Type was not

significant [F(3,168)=0.26].

To rule out possible confounding effects of the sequence

of block presentation, we conducted a secondary analysis of

variance with bsequenceQ as additional between-subjects

factor. Results did not show any significant effect of the

presentation sequence [main effect, F(3,50)=1.25; interac-

tions: Word Type�Sequence, F(9,150)=0.90; Word Type-�Group�Sequence, F(9,150)=1.32; all P’sN.15].


The implicit memory test found no main group effect

[F(1,56)=1.23]. The main effect Word Type was significant

[F(3,168)=10.05, Pb.001, partial g2=.15]. Contrast showed

that illness-related word stems were significantly more often

correctly completed than the word stems of the other three

categories [F(1,56)=10.59, Pb.01, partial g2=.16].The interaction Group�Word Type was significant

[F(3,168)=2.36, Pb.05, partial g2=.04]. To clarify the

Fig. 2. Word-stem completion in the SFD group and in the healthy

control group: the number of words (and standard error) completed

per category.


nature of the interaction (Fig. 2), separate MANOVA were

carried out for each group. In the SFD group, the effect

Word Type was highly significant [F(3,96)=11.67,

Pb.001, partial g2=.27]. Furthermore, specific contrasts

confirmed that the number of correctly completed words

was higher for illness-related words than for the other

three categories for the SFD group [F(1,32)=16.16,

Pb .001, partial g2=.34]. Paired comparisons confirmed

higher completion rates in the illness-related category than

in any of the other categories (P’sb .05). Control subjects

did not show a bias for completing illness-related word

stems more often than a bias for completing other word

stems [F(3,72)=2.15].

Additional t tests were conducted to compare the two

groups with respect to each word category and showed that

the SFD group completed more illness-related words

correctly compared to the control group [t(56)=�1.94,Pb.05, d=0.52]. The groups did not differ with respect to

the completion of negative, positive, and neutral words

[t’s(56)=0.05–1.05].

The relative implicit bias for illness-related words

(correct completion of illness-related words divided by the

overall correct completion�100) correlated with clinical

characteristics of SFDs, but did not show any significant

association with the number of lifetime somatoform

symptoms (r=.08), the number of current somatoform

symptoms (r=.05), symptom severity (r=.04), and the

degree of health anxiety (r=.06).

Post-hoc analysis for unprimed word-stem completions

To rule out a general response bias for illness-related

information in SFD subjects, we conducted the following

post-hoc analysis. An independent researcher (blinded to

study aims and design) categorized all nonhit words in the

word-stem completion task, so that the number of unprimed

words for each category could be determined. The numbers

[mean (S.D.)] of illness-related/negative/positive/neutral

words were 2.2 (1.4)/3.6 (1.7)/5.6 (2.0)/17.3 (3.9) in the

SFD group and 2.3 (1.4)/4.4 (1.8)/4.9 (2.2)/18.0 (3.7) in the

control group. Results of MANOVA with unprimed words

did not show a higher rate of illness-related words in SFD

subjects than in controls; the interaction Group�Word Type

was not significant [F(3,168)=1.1, P=.36]. This indicates

that a general response bias cannot account for the results of

the word-stem completion task.

Recognition

The second explicit memory task consisted of the

recognition of previously presented words among a word

list of primed and unprimed words. The SFD group and the

control group did not differ in their overall ability to

correctly identify the material (dV) [F(1,56)=0.40]. How-

ever, once again, a significant main effect of Word Type was

detected [F(3,168)=19.46, Pb.001, partial g2=.26]. The dVfor the recognition of illness-related words was significantly

better than the dV for the other word categories [contrast

F(1,56)=33.19, Pb.001, partial g2=.37]. The overall recog-

nition rate for illness-related words was higher than that for

words with unspecific negative, positive, or neutral content

(paired comparisons, P’sb .05).

Contrary to the hypotheses, it could not be shown that

SFD group subjects recognized illness-related words more

often than did control group subjects [Group�Word Type,

F(3,168)=0.23].

Reanalysis to control for depression severity

In a second step, a reanalysis controlling for BDI

depression (ANCOVA) was conducted. The effects of the

covariate were not significant in the free recall, recog-

nition, and word-stem completion tasks [F’s(1, 54)=0.01–

0.53]. The pattern of results across the three memory

tasks was the same as that reported in previous analyses:

no group main effects: F’s(1, 54)=0.49–1.2; significant

Word Type main effects: F(3,162)=3.4–12.2 for all tasks;

interaction Group�Word Type being significant in the

word-stem completion task only: F(3,162)=2.30 (Pb.05,

partial g2=.04.) Thus, the identified effects of the main

analyses cannot be solely explained by differences in

depression severity.

Association between memory tasks

Free-recall and recognition rates as assessed with the two

explicit memory tasks correlated significantly with each

other (r’s=.42–.67; illness related, r=.42; negative, r=.54;

positive, r=.67; neutral, r=.61). As expected, correlations

between the implicit task and the explicit tasks bfree recallQ(r’s=.16–.31; illness related, r=.16; negative, r=.24; pos-


itive, r=.31; neutral, r=.25) and brecognitionQ (r’s=.20–.41;illness related, r=.34; negative, r=.20; positive, r=.41;

neutral, r=.34) were lower.

Discussion

The main findings of the study were that individuals with

multiple somatoform symptoms showed a bias for illness-

related information in the implicit memory task, whereas

such a bias could not be revealed with the free-recall and

recognition tasks, which require more elaborative processes.

The overall memory capacity (the number of words

correctly remembered) did not differ between the two

groups in any of the tests.

In the word-stem completion task, the subjects completed

word stems with the first word that came into their mind.

Individuals with somatization syndrome filled in the

previously presented illness-related content more often than

controls. This implies that SFD subjects’ first reaction

towards an ambiguous stimulus showed the tendency to

primarily consider body-related and illness-related informa-

tion. In this respect, the finding gives support to cognitive–

behavioral models of SFDs [6,40,41] and hypochondriasis

[42,43]. All of these models emphasize the interaction of

attentional focus on health-related information and body

signals with misinterpretation of these stimuli in a cata-

strophizing manner. The role of memory is not explicitly

formulated, but can be embedded in these models [44]:

cognitive schemata about body functions, health, and illness

can influence the memory, perception, and interpretation of

associated stimuli.

The implicit bias for illness-related information was

found on a categorical level, while its association with

somatoform symptoms severity did not appear to be a linear

one (as indicated by very low correlations).

However, other explanations for the findings in the

word-stem completion task need to be considered. Stem

completion task performance might not reflect pure

implicit information processing but also explicit processes

because participants are sometimes aware that the words

they are reporting were presented during the encoding

task [45]. Based on the methods used in this study, we

were unable to disentangle the relative contribution of

implicit and explicit processes to the observed memory

task performance. Future studies should therefore

consider methods such as the bmethod of oppositionQ(e.g., see Richardson-Klavehn and Gardiner [46]) to

separate the relative contributions of implicit and

explicit processes.

The results of the implicit memory task might also be

influenced by a general response bias in SFD patients due

to a higher familiarity with illness-related stimuli. In the

present study, the word stems were derived from the

primed word list only, and we did not assess a baseline

for word completion prior to the encoding–free recall–

word-stem completion sequence, which was kept constant

across all subjects. We therefore conducted additional

post-hoc analysis with unprimed word-stem completions,

and results did not indicate that SFD subjects had a

general tendency to complete word stems with disorder-

congruent information.

Until now, there have only been a few experimental

studies on memory bias in SFDs, and overall results have

been inconsistent.

Our result of an implicit task-based bias for health-related

information confirms one previous finding. Scholz et al.

[22] reported an implicit, but not explicit, information-

processing bias in subjects with multiple somatoform

symptoms. Contrary to our result, Lim and Kim [23], using

a tachistoscopic word-identification task, did not show

differential patterns of implicit memory across the SFD,

depressive, and panic groups. The absence of implicit

memory biases in this study may be explained by the nature

of this task. As Watkins [47] has argued, an implicit mood-

congruent memory bias does not appear to exist when

perceptually driven tests are used.

We were unable to demonstrate a bias for illness-related

words with the explicit memory tasks of free recall and

recognition. This is in accordance with some previous

findings [18,21,22] but is in contrast to some others

[19,20,23]. Rief et al. [21] did not show a recall bias for

illness-related words in a sample of patients suffering from

multiple somatoform symptoms. The characteristics of the

clinical sample were similar to those of the somatization

syndrome group in our study. Two other studies that

provided some support for an explicit bias included

samples characterized by hypochondriac anxiety [19,20].

It is possible that the inconsistent findings are a result of

sample characteristics, as the group of SFDs covers a

range of heterogeneous disorders; in other words, perhaps

the variety of SFDs suggests different and varied

information-processing biases. Current cognitive models,

however, do not sufficiently differentiate between diag-

noses within the spectrum of SFDs, as has been shown in

anxiety disorders [48].

The previously mentioned study of Lim and Kim [23]

showed a higher free-recall ratio of physical threat words

for SFD patients to physical threat words for healthy

controls. However, memory results were confounded by

reduced memory capacity in SFD patients compared to

controls. In our study, both samples showed comparable

memory capacity, and the overall recall rate appeared to

be higher than that in Lim and Kim. Thus, these

variations might account for the different results on

explicit memory bias. Further studies are needed to

appraise the role of explicit memory processes across

variations in stimulus sets and experimental paradigms in

various SFDs.


In the present study, we chose an established

paradigm to assess disorder-specific information-process-

ing bias. However, one might object that confrontation

with word stimuli, followed by subsequent memory

tasks, lacks some ecological validity. It is possible that

memory biases in SFDs appear especially with current

ambiguous events. For example, a recent study showed

that patients with somatization syndrome remembered

increased likelihood estimates of medical causes for body

symptoms, which had been presented in audiotaped

medical records [49].

Further shortcomings of the present study need to be

mentioned. The clinical sample consisted of a group of

patients suffering from somatization syndrome (SSI-3/5),

and the diagnostic procedure relied on self-report data.

Although the instrument (SOMS-2) has been shown to be

considerably sensitive to the detection of SFDs [24,25], a

diagnostic procedure using an interview and medical

assessment to rule out organic symptom causation would

have been preferable. Against the rather liberal criterion

of intake we used in our study, the mean number of

somatoform symptoms (lifetime symptoms, 15; current

symptoms, 5) was much higher. The diagnostic group

characterized by multiple somatoform symptoms is gen-

erally considered to be a very relevant group in the health

care system [2,50].

Even though the sample size of our study was

comparable to or even higher than those in most reference

studies [8–20,22], it limits statistical power to detecting

small effects. However, inspection of the recall and

recognition rates per group and category does not at all

suggest any interaction between group and word type.

Interpretation of the results is further limited by the

absence of a clinical control group. Therefore, it cannot be

determined whether the obtained results were specific to

SFDs. This needs to be investigated in future studies. To

rule out a confounding influence of depression, we

reanalyzed the data; the result pattern persisted even when

controlling for depression.

The choice of the stimulus material for the present study

was subject to a rigorous process: word lists were matched

for word length and frequency, and emotional valence was

comparable for illness-related and unspecific negative

words. Because of ground effects in previous studies, we

asked subjects to memorize the words by relating them to

subjectively relevant events. This encoding strategy could

have been more effective in SFD patients as they

presumably had more past health-related events. Still,

both groups showed comparable memory capacity, and

especially the two explicit tasks did not reveal a

memory bias in the SFD group. In our study, memory

for illness-related words was contrasted with memory

for general negative, positive, and neutral words. To

investigate the specificity of a bias for (threatening)

illness-related stimuli, it might be worth including

positive health-related stimuli in future studies.

To summarize, the results suggest a disorder-congruent

information-processing bias in somatization syndrome,

appearing in a task that reflects more automatic encoding

and does not need deep elaboration. A general tendency to

better recall disorder-related information in explicit mem-

ory tests was not shown. Overall, the results provide some

support for the cognitive model of SFDs. The identifica-

tion of particular maladaptive information-processing

strategies could lead to a better understanding of the

nature of SFDs. However, as the body of evidence is still

very limited and inconclusive, there is still an obvious

need for further research.

References

[1] Barsky A, Ettner SL, Horsky J, Bates DW. Resource utilization of

patients with hypochondriacal health anxiety and somatization. Med

Care 2001;39:705–15.

[2] Creed F, Barsky A. A systematic review of the epidemiology of

somatisation disorder and hypochondriasis. J Psychosom Res

2004;56:391–408.

[3] Jyv7sj7rvi S, Joukamaa M, V7is7nen E, Larivaara P, Kivel7 S-L,

Kein7nen-Kiukaanniemi S. Somatizing frequent attenders in primary

health care. J Psychosom Res 2001;50:185–92.

[4] Nanke A, Rief W. Zur Inanspruchnahme medizinischer Leistungen bei

Patienten mit somatoformen Stfrungen. Psychotherapeut 2003;

48:329–35.

[5] Barsky AJ. Amplification, somatization, and the somatoform disor-

ders. Psychosomatics 1992;33:28–34.

[6] Rief W, Nanke A. Somatization disorder from a cognitive–psycho-

biological perspective. Curr Opin Psychiatry 1999;12:733–8.

[7] Warwick HMC. A cognitive–behavioural approach to hypochondria-

sis and health anxiety. J Psychosom Res 1989;33:705–10.

[8] Salkovskis PM, Warwick HMC. Meaning, misinterpretations, and

medicine: a cognitive–behavioural approach to understanding health

anxiety and hypochondriasis. In: Starcevic V, Lipsitt DR, editors.

Modern perspectives on an ancient malady. Oxford7 University Press,

2002. pp. 203–22.

[9] Barsky AJ, Coeytaux RR, Sarnie MK, Cleary PD. Hypochondriacal

patient’s beliefs about good health. Am J Psychiatry 1993;150:1085–9.

[10] Rief W, Hiller W, Margraf J. Cognitive aspects in hypochondriasis and

the somatization syndrome. J Abnorm Psychol 1998;107:587–95.

[11] Rief W, Nanke A, Emmerich J, Bender A, Zech T. Causal illness

attributions in somatoform disorders—associations with comorbidity

and illness behavior. J Psychosom Res 2004;57:367–71.

[12] Williams JMG, Watts FN, MacLeod C, Mathews A. Cognitive

psychology and emotional disorders. New York7 Wiley, 1988.

[13] Williams JMG, Watts FN, MacLeod C, Mathews A. Cognitive

psychology and emotional disorders. 2nd ed. Chichester7Wiley, 1997.

[14] MacLeod C, McLaughlin K. Implicit and explicit memory bias in

anxiety: a conceptual replication. Behav Res Ther 1995;33:1–14.

[15] Mathews A, Mogg K, May J, Eysenck M. Implicit and explicit

memory bias in anxiety. J Abnorm Psychol 1989;98:236–40.

[16] Watkins PC, Mathews A, Williamson DA, Fuller RD. Mood-

congruent memory in depression: emotional priming or elaboration?

J Abnorm Psychol 1992;101:581–6.

[17] Pincus T, Morley S. Cognitive-processing bias in chronic pain: a

review and integration. Psychol Bull 2001;127:599–617.

[18] Durso FT, Reardon R, Shore WJ, Delys SM. Memory processes and

hypochondriacal tendencies. J Nerv Ment Dis 1991;179:279–83.

[19] Brown HD, Kosslyn SM, Delamater B, Fama J, Barsky AJ. Perceptual

and memory biases for health-related information in hypochondriacal

individuals. J Psychosom Res 1999;47:67–78.


[20] Pauli P, Alpers GW. Memory bias in patients with hypochondriasis

and somatoform pain disorder. J Psychosom Res 2002;52:45–53.

[21] Rief W, Shaw R, Fichter MM. Elevated levels of psychophysiological

arousal and cortisol in patients with somatization syndrome. Psycho-

som Med 1998;60:198–203.

[22] Scholz OB, Ott R, Mqller-Sinik K. Beziehungen zwischen

Parametern der impliziten und expliziten Informationsverarbeitung

und psychosomatischen Selbstberichtsmagen. Verhaltenstherapie

1997;7:217–25.

[23] Lim S-L, Kim J-H. Cognitive processing of emotional information in

depression, panic, and somatoform disorder. J Abnorm Psychol

2005;114:50–61.

[24] Rief W, Heuser J, Mayrhuber E, Stelzer I, Hiller W, Fichter MM. The

classification of multiple somatoform symptoms. J Nerv Ment Dis

1996;184:680–7.

[25] Rief W, Hiller W, Heuser J. SOMS—Das Screening fqr Somatoforme

Stfrungen Manual zum Fragebogen [SOMS—The Screening for

Somatoform Symptoms]. Bern7 Huber-Verlag, 1997.

[26] Escobar JI, Rubio-Stipec M, Canino G, Karno M. Somatic Symptoms

Index (SSI): a new and abridged somatization construct—prevalence

and epidemiological correlates in two large community samples.

J Nerv Ment Dis 1989;177:140–6.

[27] Rief W, Hiller W. A new approach to the assessment of the treatment

effects of somatoform disorders. Psychosomatics 2003;44:492–8.

[28] Pilowsky I. Dimensions of hypochondriasis. Br J Psychiatry 1967;

113:89–93.

[29] Rief W, Hiller W, Geissner E, Fichter MM. Hypochondrie: Erfassung

und erste klinische Ergebnisse. Z klin Psychol 1994;23:34–42.

[30] Hiller W, Rief W. Internationale Skalen fqr Hypochondrie. Bern7 HansHuber, 2004.

[31] Speckens AEM, Van A, Hemert M, Spinhoven P, Bolk JH. The

diagnostic and prognostic significance of the Whitely Index, the

Illness Attitudes Scales and the Somatosensory Amplification Scale.

Psychol Med 1996;26:1085–90.

[32] Beck AT, Steer RA. Beck Depression Inventory Manual. San Antonio7

The Psychological Cooperation, 1987.

[33] Hautzinger M, Bailer M, Worall H, Keller F. Beck Depressionsin-

ventar: 2 Aufl. Bern7 Huber, 1995.

[34] Beck AT, Steer RA, Garbin MG. Psychometric properties of the Beck

Depression Inventory: twenty-five years of evaluation. Clin Psychol

Rev 1988;8:77–100.

Word type [English translation (original German material)]

Illness related Negative

Illness (Krankheit) Loss (Verlust)

Surgery (Operation) Disaster (Katastrophe)

Disease (Erkrankung) Failure (Versagen)

Drug (Medikament) Insult (Beleidigung)

Headache (Kopfschmerzen) Ignorance (Ignoranz)

Stroke (Schlaganfall) Jealousy (Eifersucht)

Infection (Ansteckung) Bitterness (Bitterkeit)

Migraine (Migr7ne) Ozone hole (Ozonloch)

Breathlessness (Atemnot) Pollution (Verschmutzung)

Heart attack (Herzanfall) Rage (Wutausbruch)

Cancer (Krebs) War (Krieg)

Joint pain

(Gelenkschmerzen)

Spitefulness

(Geh7ssigkeit)

Appendix. Word stimuli, by category

[35] Lehrl S. Mehrfachwahl-Wortschatz-Intelligenztest (MWT-B). Baling-

en7 Spitta Verlag, 1977.

[36] Satzger W, Fessmann H, Engel RR. Liefern HAWIE-R, WST und

MWT-B vergleichbare IQ-Werte? Z Differ Diagn Psychol 2002;

23:159–70.

[37] Shaw R. Psychologische und psychophysiologische Aspekte somato-

former Stfrungen. Marburg7 Tectum Verlag, 1996.

[38] Ehlers A, Margraf J. Fragebogen zu kfrperbezogenen Angsten,

Kognitionen und Vermeidung. Weinheim7 Beltz Test, 1993.

[39] Hathaway SR, McKinley JR, Engel RR. Minnesota Multiphasic Per-

sonality Inventory—Revised (MMPI-2) Manual. Bern7 Huber, 2000.

[40] Kirmayer LJ, Taillefer S. Somatoform disorders. In: Turner SM,

Hersen M, editors. Adult psychopathology and diagnosis. New York7

John Wiley, 1997. pp. 338–83.

[41] Sharpe M, Bass C. Pathophysiological mechanisms in somatization.

Int Rev Psychiatry 1992;4:81–97.

[42] Barsky AJ, Wyshak GL. Hypochondriasis and somatosensory

amplification. Br J Psychiatry 1990;157:404–9.

[43] Salkovskis PM, Warwick HMC. Morbid preoccupations, health

anxiety and reassurance: a cognitive–behavioural approach to

hypochondriasis. J Psychosom Res 1986;24:597–602.

[44] Brown RJ. Psychological mechanisms of medically unexplained

symptoms: an integrative conceptual model. Psychol Bull 2004;

130:793–812.

[45] Schacter DL, Bowers J, Booker J. Intention, awareness, and implicit

memory: the retrieval intentionality criterion. In: Lewandowsky S,

Dunn JC, Kirsner K, editors. Implicit memory: theoretical issues.

Hillsdale (NJ)7 Erlbaum, 1989. pp. 47–65.

[46] Richardson-Klavehn A, Gardiner JM. Retrieval volition and memorial

awareness in stem completion: an empirical analysis. Psychol Res

1995;87:252–71.

[47] Watkins PC. Implicit memory bias in depression. Cogn Emot

2002;16:381–402.

[48] Coles ME, Heimberg RG. Memory biases in the anxiety disorders:

current status. Clin Psychol Rev 2002;22:587–627.

[49] Rief W, Heitmqller AM, Reisberg K, Rqddel H. Why reassurance fails

in patients with unexplained symptoms—an experimental investiga-

tion of remembered probabilities. PLoS Med 2006;3:e269 [7 pp].

[50] Escobar JI, Golding JM, Hough RL, Karno M, Burnam MA, Wells

KB. Somatization in the community: relationship to disability and use

of services. Am J Public Health 1987;77:837–40.

Positive Neutral

Peace (Frieden) Paper (Papier)

Justice (Gerechtigkeit) Entrance (Eintritt)

Confidence (Zuversicht) Second (Sekunde)

Leisure time (Feierabend) Front door (Haustqr)Compliment (Kompliment) Encyclopedia (Lexikon)

Affection (Zuneigung) Borough (Stadtbezirk)

Brightness (Helligkeit) Cassette (Kassette)

Summertime (Sommerzeit) Carpet (Teppich)

Tenderness (Z7rtlichkeit) Ballpen (Kugelschreiber)

Heartiness (Herzlichkeit) Rooftile (Dachziegel)

Beach (Strand) Cupboard (Schrank)

Amusement

(Vergnuglichkeit)

Mashed potatoes

(Kartoffelbrei)

Memory bias for health-related information in somatoform disorders

Documents

Transcript of Memory bias for health-related information in somatoform disorders