Evaluation of a motivational interview for substance use within psychiatric in-patient services

© 2002 Society for the Study of Addiction to Alcohol and Other Drugs Addiction, 97, 1329–1337

INTRODUCTION

It is well recognized that there are high rates of com-orbidity of mental illness and substance use disorders.The low prevalence disorders study component of theNational Survey of Mental Health and Well-being inAustralia showed that 34% of males and 46% of femaleswith an alcohol-use disorder also had at least one othermental disorder (Teesson et al. 2000). Among peoplewith psychotic disorders, a life-time diagnosis of alcohol-use disorder was found in 38.7% of males and 17% offemales, with corresponding figures of 36.3% and 15.7%for a life-time diagnosis of drug abuse/dependence(Jablensky et al. 1999). A recent Australian psychosis

study comparing different recruitment sources (generalpractices and in-patient and community mental healthservices) also found pervasive substance use problemsdespite substantial group differences in symptomatologyand functioning (Carr et al. 2002). In a review of 47studies of prevalence rates of substance use amongpeople with schizophrenia, Cantor-Graae and colleagues(Cantor-Graae, Nordstrom & McNeil 2001) reported life-time rates of substance abuse ranging between 40 and60%. People with comorbid mental illness and substanceuse disorders tend to have a poorer prognosis, are morelikely to develop chronic and disabling conditions, andhave greater service utilization (Teesson & Gallagher1999).

Evaluation of a motivational interview for substanceuse within psychiatric in-patient services

Amanda Baker1, Terry Lewin1,2, Heidi Reichler1, Richard Clancy2, Vaughan Carr1,2,Rachel Garrett1, Ketrina Sly1, Holly Devir1 & Margarett Terry2

Centre for Mental Health Studies, University of Newcastle1 and Hunter Mental Health, Newcastle, New South Wales, Australia2

ABSTRACT

Aims To assess the effectiveness of a motivational interview among hospi-talized psychiatric patients with comorbid substance use disorder in reduc-ing alcohol and other drug (AOD) use.Design Subjects were assigned randomly to receive an individual motiva-tional interview (n = 79) or a self-help booklet (control condition; n = 81).Setting Subjects were volunteers recruited from a major public psychiatrichospital.Participants Subjects met abuse or dependence criteria on the structuredclinical interview for diagnosis (SCID) for alcohol, cannabis or ampheta-mine or they reported hazardous use during the last month of one or moreof these drug types on the opiate treatment index (OTI).Intervention Either one 30–45-minute motivational interview or briefadvice.Measurements The SCID and OTI were the main measures.Findings There was a modest short-term effect of the motivational inter-view on an aggregate index of alcohol and other drug use (polydrug use on the OTI). Cannabis use remained high among the sample over the 12-month follow-up period.Conclusion Although motivational interviewing appears feasible amongin-patients in psychiatric hospital with comorbid substance use disorders,more extensive interventions are recommended, continuing on an out-patient basis, particularly for cannabis use.

KEYWORDS Brief intervention, comorbidity, dual diagnoses, motivationalinterview, treatment.

RESEARCH REPORT

Correspondence to:

Amanda BakerCentre for Mental Health StudiesUniversity of NewcastleUniversity DriveCallaghan, NSW 2308AustraliaTel: + 61 2 49246610Fax: + 61 2 4924 6608E-mail: [email protected]

Submitted 21 September 2001;initial review completed 5 December 2001;final version accepted 1 March 2002

1330 Amanda Baker et al.


Despite the high prevalence of comorbidity and itsburden, there is a paucity of research evaluating theeffectiveness of interventions for alcohol and other drug(AOD) use among people with coexisting mental illnessand substance use disorders. In their Cochrane review ofavailable interventions with these disorders, Ley et al.(2001) concluded that existing research is methodologi-cally weak and that randomized controlled trials need tobe conducted.

Recently, two randomized controlled trials haveaddressed AOD use among people with psychoses.Martino and colleagues (Martino et al. 2000) conducteda pilot study in which 23 people with either mood or psy-chotic disorders and comorbid substance abuse/depen-dence were assigned randomly to either a motivationalinterview or standard interview prior to participation in a 12-week partial hospital programme. Subjects who received a motivational interview attended the pro-gramme for significantly more days compared to patientsin an historical control group, with standard interviewsubjects’ attendance falling between the two conditions.Subjects who had received motivational interviewingwere also less tardy in their attendance and had fewerearly departures.

Barrowclough and colleagues (Barrowclough et al.2001) compared routine care with a programme ofroutine care integrated with motivational interviewing(five weekly sessions), cognitive-behavioural therapywith further motivational interviewing (24 sessions) andfamily or carer intervention (10–16 sessions) among 36patients with schizophrenia and substance use disordersand their carers. At 3-month follow-up, the integratedtreatment resulted in significantly greater improvementin patients’ general functioning and lower scores on positive symptoms compared to the control group. Thepercentage of days abstinent from all substances over the12-month study period was greater for the integratedgroup. The authors suggested that the relative efficacy ofthe components of the integrated intervention should bethe subject of further research.

There is evidence that brief interventions can be effec-tive in the treatment of alcohol problems (Bien, Miller &Tonigan 1993) and as preparation for further AOD treat-ment (Bien, Miller & Boroughs 1993; Brown & Miller1993). However, it also appears that more intensive interventions benefit alcohol-dependent patients andthat structured and scheduled follow-up should be avail-able (Mattick & Jarvis 1993). Furthermore, Heather(1995) has argued that evidence for the effectiveness ofbrief intervention is much stronger in the area of oppor-tunistic interventions in the non-treatment-seeking pop-ulation than for brief intervention in specialist settingsfor those seeking help with AOD use. The present studywas designed to evaluate the effectiveness of a motiva-

tional interview (MI) for in-patients in a psychiatric hos-pital with comorbid substance use problems. The MIaimed to: (i) enhance engagement in an out-patient spe-cialist substance misuse service (SSMS) for people withcomorbid mental illness and AOD problems (therebyaccessing a lengthier intervention), and (ii) to reduceAOD use. In a previous paper (Baker et al. 2002) weaddressed the issue of whether the MI enhanced engage-ment in a SSMS. The intervention failed to achieve this,with only 16.9% attending the service within the first 3months post-intervention. It was recommended thattreatment should be integrated fully so that cliniciansfrom within the same service could monitor and addressmental health problems and AOD use.

The present paper focuses on the effectiveness of theMI in changing short-term and medium-term AOD use,and on documenting 12-month substance use profilesamong those with comorbid mental health and sub-stance use problems. It was hypothesized that the MIwould be more effective than a brief advice control con-dition in reducing AOD use, symptomatology and drug-related harms 3, 6 and 12 months after the intervention.

DESIGN

Subjects were allocated randomly to either an MI or to a control group. Assessments of AOD use and sympto-matology were scheduled at pre-treatment and 3, 6 and12 months following the pre-treatment assessment. Aninterviewer blind to subjects’ group allocation conductedfollow-up assessments.

Subjects

The subjects were in-patients of an acute public psychi-atric hospital in the Hunter region of New South Wales,Australia. Patients were identified as potentially suitablefor the study either through their medical records and/orby direct referral to the study from hospital staff.Inclusion criteria were: in-patient status in the psychi-atric hospital, capable of interview, likely to reside in thelocal geographical region during the next 12 months andconsumption of AOD during the months prior to admis-sion at a sufficient level to warrant the intervention.Intervention threshold for AOD consumption at pre-treatment was defined as meeting diagnostic criteria forcurrent (past 6 months) abuse or dependence on thestructured clinical interview for DSM-III-R (SCID; Spitzeret al. 1990), the use of any illicit drug on a weekly basis(or the equivalent score of 0.14 or higher on the drug use scale of the opiate treatment index (OTI; Darke et al.1991) in the month prior to interview, or alcohol consumption exceeding recommended National Health

Motivational interview among psychiatric in-patients 1331


and Medical Research Council (NHMRC) levels, namelyfour standard drinks per day for men and two for women(Pols & Hawks 1992). One hundred and sixty patientsmet recruitment criteria and were assessed betweenSeptember 1996 and July 1998. All subjects were volun-teers and were paid a nominal amount ($20) for atten-dance at each assessment session. The amount wasassumed to be small enough not to influence response tothe intervention but adequate to reduce non-compliancecaused by any inconvenience in attending sessions.

Procedure

A few days after hospital admission, subjects were invitedto participate in a longitudinal study of substance abuseamong people with mental illness. The purpose, designand components of the study were described to thesepatients and they were told that, on giving writteninformed consent to enter the study, they would beassigned randomly to either one session of counselling or to receive information about AOD use. Subjects wereassured that any information they gave to researcherswas confidential and that refusal to participate would notaffect their relationship with the mental health service inany way. Interviews took 1.5–2 hours to complete.

Measures

The instruments used have been documented in anearlier paper (Baker et al. 2002) and are described onlybriefly here. The alcohol use disorders and non-alcoholpsychoactive substance use disorders sections of the SCID(Spitzer et al. 1990) were used to determine life-time andcurrent (past 6 months) substance abuse or dependence.They were administered at pre-treatment and at 6- and12-month follow-ups. The OTI (Darke et al. 1991) wasused to assess consumption of 11 classes of drug duringthe month preceding interview (including the admissionperiod at pre-treatment) on all assessment occasions. TheOTI was also used to measure social functioning andcrime at pre-treatment and 6- and 12-month follow-ups.All measurements on the OTI pertained to the 1-monthperiod prior to interview except for the social scale, whichassessed the 6 months prior to interview.

Psychiatric diagnoses were determined by the respon-sible clinicians and obtained from the patients’ medicalrecords. The DSM-IV (American Psychiatric Association1994) Axis 1 discharge diagnoses were subsequently collapsed to create the following (non-substance use) categories: schizophrenia; mood disorder; other; andnone. Psychiatric symptomatology was assessed via thebrief symptom inventory (BSI) general severity index(Derogatis & Melisaratos 1983). The BSI was adminis-tered on all assessment occasions.

A 10-rung contemplation ladder (Biener & Abrams1991) was used at pre-treatment as a measure of readi-ness to change each category of AOD used in the monthprior to interview. Because subjects’ responses were clus-tered around the five rungs with verbal anchors, the cat-egories were collapsed subsequently as follows: 0: ‘Nothought of quitting or cutting down’; 1: ‘Think I need toconsider quitting or cutting down someday’; 2: ‘Think Ishould quit or cut down but not quite ready’; 3: ‘Startingto think about how to change my drinking/using pat-terns’; and 4: ‘Taking action to quit or cut down’. Anaggregate score was also determined and used as a pre-dictor variable in analyses which did not relate to one specific drug type. This was calculated by averaging stage of change scores for substances for which subjectsmet intervention threshold.

Motivational interview

The main aims of the MI were to reduce AOD use and toincrease participation in the SSMS. The MI and its effectson participation in a SSMS have been reported previously(Baker et al. 2002) and its content are described onlybriefly here. The MI (Miller & Rollnick 1991) occurredimmediately following the preintervention assessment,was conducted individually and lasted 30–45 minutes. A therapist manual guided the sessions and a leaflet summarizing the session was given to the patient uponits conclusion. A harm reduction approach was takenwhereby individuals chose their own goals, if any, forchanging one or more drug classes. Subjects were pro-vided with feedback regarding their current levels of AODconsumption and the positive and negative aspects ofAOD use were discussed. Possible factors contributing to AOD use were also discussed, concerns identified andeducation was provided interactively about safer con-sumption levels. The therapist aimed to follow thisprocess with each substance used by the subject. Nicotinereduction was not targeted in this study, as a specific anddifferent intervention would have been needed. When asubject showed evidence of having arrived at the deter-mination or action stages of change (Miller & Rollnick1991; Prochaska & DiClemente 1986), potentially bene-ficial cognitive-behavioural coping strategies were dis-cussed. Subjects were encouraged to identify previouslysuccessful and unsuccessful coping attempts. Successfulstrategies were encouraged (e.g. avoiding other users andcertain places) and new strategies identified (e.g. attend-ing the SSMS). Strategies for coping with lapses (Marlatt& Gordon 1985) were discussed.

Control group subjects were informed that they wereusing substances at a hazardous level and that theyshould reduce their consumption to safer levels. All sub-jects (i.e. intervention and control conditions) were then



accompanied to the SSMS, given a description of theservice, introduced to the receptionist, encouraged toattend and provided with a pamphlet about the service.An entry was made in each subject’s medical record thatthey had been encouraged to attend the service.

The therapists were four psychologists with honoursdegrees in psychology. The first author provided both initial training and weekly supervision in motiva-tional interviewing and cognitive-behavioural copingstrategies.

Patterns of participation

Although there were similar participation rates at the 3-, 6- and 12-month follow-ups (70.0%, 73.1%; 71.9%,respectively) only 89/160 subjects (55.6%) completed all follow-up phases. Four people died between pre-treatment and the 3-month follow-up and a further twodied between 3- and 6-month follow-up assessments.There were no significant differences between subjectswho completed all follow-up assessments (n = 89), somefollow-up assessments (n = 47) or no follow-up assess-ments (n = 24) on key variables of interest: interventionallocation; age; gender; living arrangements; employ-ment; marital status; DSM-IV Axis 1 diagnosis; SCIDdiagnoses of abuse or dependence versus no diagnoses foralcohol, cannabis, amphetamines or benzodiazepines;and length of stay in hospital in the 12 months prior tothe index admission. There were 55 MI and 57 controlsubjects at 3-month follow-up and 43 MI and 46 controlsubjects who completed all assessment occasions.

Statistical analysis

Data were analysed using SPSS for Windows (version10). Owing to variations in participation patterns, therestricted set of measures at 3-month follow-up and thepossibility of shorter-term benefit from a MI, we con-ducted two sets of analyses: those based on the 112 sub-jects who completed pre-treatment and the 3-monthfollow-up; and those based on the 89 subjects who com-pleted all four occasions. Initially, 2 ¥ 2 ¥ (2) repeated-measures analyses of covariance (ANCOVAs) wereconducted to assess the contribution of stage of change(i.e. action stage of change versus early stage of change)and intervention status (control versus intervention) tochanges between the pre-treatment assessment and the3-month follow-up. The two covariates were length ofhospital admission during the follow-up period andattendance at the SSMS. There were two subsets of con-tinuous dependent variables in the initial analysis: thosefor which all subjects had a score (polydrug use andscores on the BSI); and those for which usage thresholds

applied (OTI scores for those substances that were abovethe intervention threshold for the individual and at least20% of the sample; alcohol, cannabis and ampheta-mines). Subsequently, 2 ¥ 2 ¥ (4) repeated-measuresANCOVAs were conducted (stage of change by interven-tion status by time) to examine patterns of differenceacross all four occasions of measurement. Similar covari-ates were used in these analyses but in this instance theyreferred to the entire follow-up period. The same variablesused in the initial analysis were analysed in addition toscores on social dysfunction and crime (all subjects) andnumber of substances for which they met SCID abuse or dependence criteria during the last 6 months (usagethresholds applied). Scheffé follow-up comparisons wereconducted if the overall ANCOVA was significant.Categorical variables were analysed using c2 tests. As a partial control for the number of statistical tests, athreshold for significance of P < 0.01 was adopted.

RESULTS

Sample characteristics

The sample comprised 160 psychiatric in-patients withcoexisting AOD problems. Overall pre-treatment samplecharacteristics and patterns of drug use have beenreported elsewhere (Baker et al. 2002). As documented in the previous paper (Baker et al. 2002), 90% of the 160subjects (n = 144) reported current (past 6 months) sub-stance abuse or dependence on the SCID, 89.4% (n = 143)reported at least weekly consumption of AOD on the OTI,while 79.4% (n = 127) met both inclusion criteria.Intervention criteria were met by the following propor-tions of the sample: 60.6% for alcohol; 66.3% forcannabis; and 22.5% for amphetamines. The main pre-treatment characteristics of the control and interventiongroups are shown in Table 1. Analysis of pre-treatmentdata on the key variables identified above indicated thatthere were no significant differences. The majority ofthe subjects were male, with numerous admissions to apsychiatric hospital and over half of the sample had previously been treated for substance abuse.

Changes in drug use and symptomatology between pre-treatment and 3-month follow-up

Mean pre-treatment, 3-month follow-up and changescores are reported in Table 2 for: polydrug use; the threemost commonly used drugs, alcohol, cannabis andamphetamines; and scores on the BSI.

Overall, the repeated measures ANCOVAs revealedsignificant main effects for time (pre-treatment to 3-month follow-up) for polydrug, alcohol and cannabis use



but not for amphetamine use (F1,15 = 0.10, NS). Therewere no significant group or stage of change main effects.Polydrug, alcohol and cannabis use fell significantly forthe sample as a whole (F1,105 = 9.52, P < 0.01;F1,60 = 8.07, P < 0.01; F1,71 = 7.87, P < 0.01, respectively).There was a (non-significant) tendency for the reductionin polydrug use to be greater among the MI group com-pared to the control group (F1,105 = 4.47, P = 0.04). Whilenot statistically significant, the mean number of drugclasses used during the month prior to assessment fell0.42 units among the control group versus 0.93 unitsamong the MI group, equivalent to a drop of approxi-mately a half versus one class of drug. Expressed in effectsize units (0.32 versus 0.70), this represents a differenceof 0.38 of a standard deviation, a modest but potentiallyimportant difference.

The repeated-measures ANCOVA revealed a signifi-cant main effect for time (pre-treatment to 3-monthfollow-up) for global severity index scores on the BSI (F1, 105 = 14.13, P < 0.001). However, there were no sta-tistically significant differences between groups on theBSI. There was a significant main effect for stage of

change (F1,105 = 8.68, P < 0.01) with precontemplatorsreporting higher symptomatology scores.

Changes in drug use, symptomatology, socialfunctioning and crime across all phases

Table 3 shows changes in drug use, symptomatology,social functioning and crime at 3-, 6- and 12-monthfollow-ups. First, results are reported for continuousdependent variables for which all subjects had a score (i.e.number of substances for which they met SCID abuse ordependence criteria during the last 6 months; OTI scoresfor polydrug use, social functioning and crime; and scoreson the BSI). Also shown in Table 3 are results for depen-dent variables for which usage thresholds applied (i.e. OTIscores for those substances that were used at interventionthreshold levels and by at least 20% of the sample, namely,alcohol, cannabis and amphetamines and presence ofabuse/dependence as measured by the SCID). There wereno group differences on any of these variables.

A significant main effect for time was found for thenumber of substances for which subjects met SCID abuse

Table 1 Pre-treatment sample characteristics by group (n = 160).

Control group Intervention group(n = 81)a (n = 79)a

Male 75.3% (n = 61) 74.7% (n = 59)Mean age (SD, range) 30.05 (10.65, 16–70) 31.71 (9.77, 16–59)Married or cohabiting 16.0% (n = 13) 12.7% (n = 10)Completed upper high school 9.9% (n = 8) 7.6% (n = 6)Receiving pension or benefits 83.9% (n = 68) 68.3% (n = 54)Mean number of prior psychiatric hospital admissions (SD, range) 4.15 (6.78, 0–45) 4.51 (8.86, 0–55) (n = 79)Previous treatment for substance abuse 53.1% (n = 43) 58.2 (n = 46)Attended specialist treatment service (STS) in past 24.7% (n = 20) 35.4 (n = 28)

Psychiatric hospital admissions during the previous 12 monthsAt least one admission 35.8% (n = 29) 40.5% (n = 32)Mean number of admissions (SD, range) 2.38 (3.63, 1–20) 2.75 (2.91, 1–13)Average total admission days (SD, range) 25.17 (26.74, 1–103) 37.75 (37.63, 1–181)

Index admissionPrimary DSM-IV non-substance Axis 1 discharge diagnosis (n = 157)Schizophrenia 37.0% (n = 30) 36.7% (n = 29)Mood disorder 29.6% (n = 24) 27.8% (n = 22)Other 12.3% (n = 10) 13.9% (n = 11)Noneb 19.8% (n = 16) 19.0% (n = 15)Average length of admission (days) (SD, range) 12.21 (13.36, 1–67) 15.80 (13.30, 1–56)

SCID diagnosis of abuse or dependenceAlcohol 48.1% (n = 39) 60.8% (n = 48)Cannabis 54.3% (n = 44) 46.8% (n = 37)Amphetamine 21.0% (n = 17) 22.8% (n = 18)Benzodiazepine 11.1% (n = 9) 11.4% (n = 9)

a Tabled values are percentages (and frequencies) or mean scores (with standard deviations).b These subjects did not have a non-substance Axis 1 discharge diagnosis recorded in their medical records. However, they were retained because they hadsimilar scores on the BSI severity index to the other diagnostic groups.



or dependence criteria (F2,92 = 5.49, P < 0.01). There wasa progressive reduction in the number of SCID sub-stances for which subjects met abuse or dependence cri-teria. Only one follow-up comparison between occasionsachieved statistical significance, from pre-treatment to12-month follow-up (F1,93 = 10.96, P < 0.01). There wasa significant progressive improvement in social function-ing over time (F2,92 = 5.78, P < 0.01), with the improve-ment between pre-treatment and 6-month follow-up(F1,93 = 8.26, P < 0.01) and between pre-treatment and12-month follow-up (F1,93 = 10.87, P < 0.01) being statistically significant. There was no reduction in crimeover time (F2,92 = 0.73, NS). There was a significantimprovement in symptomatology over time as measuredby the global severity index of the BSI (F3,76 = 15.67, P < 0.001). Follow-up comparisons between pre-treatment and 3-month follow-up (F1,79 = 21.16, P < 0.001), pre-treatment and 6-month follow-up(F1,79 = 47.06, P < 0.001), pre-treatment and 12-monthfollow-up (F1,78 = 26.35, P < 0.001) were all significant.

Also shown in Table 3 are the proportions of subjectswho continued to meet SCID criteria for abuse or depen-dence, having met SCID criteria for abuse or dependenceon alcohol, cannabis or amphetamine at pre-treatment.There was a trend for more people in the MI group to

meet SCID criteria for alcohol abuse or dependence compared with the control group (c2

1 = 6.34, P = 0.02)at 6-month follow-up but this trend did not continue at 12 months (c2

1 = 0.59 (NS). At 12-month follow-up,the percentages of people who continued to meet criteria for intervention (having done so at pre-treatment) for alcohol, cannabis and amphetamine were: 48.4%; 74.7% and 24.0%, respectively. Of thesample as a whole, the percentages of people who metintervention criteria at 12-month follow-up were 33.0% for alcohol; 52.2% for cannabis; and 12.2% foramphetamines.

A small group (n = 19) of cannabis users was identi-fied who initially met intervention threshold but whowere virtually abstinent at 12-month follow-up. By com-parison there were 56 cannabis users who continued touse at levels above the intervention threshold. We wereunable to identify any variables that differentiated thesegroups.

There was a significant main effect for stage of changeon the BSI, with precontemplators reporting highersymptomatology scores (mean 1.45 versus 0.96;F1,78 = 9.67, P < 0.01). There was also a non-significanttrend for precontemplators to report higher polydrug usescores (2.98 versus 2.54; F1,80 = 5.98, P = 0.02).

Table 2 Selected OTI pre-treatment, follow-up and change indices by treatment group among subjects meeting intervention threshold criteria.

Mean OTI score (SD)

OTI drug use 3-month Standardized changeb

category Groupa n Pre-treatment follow-up Change (effect size units)

Polydrug use C 57 3.37 (1.23) 2.95 (1.46) 0.42 (1.34) 0.32(out of 11) MI 55 3.29 (1.24) 2.36 (1.16)† 0.93 (1.29) 0.70

Overall 112 3.33 (1.23) 2.66 (1.35)* 0.67 (1.33) 0.50

Alcohol C 30 9.49 (11.28) 2.99 (7.30) 6.50 (12.15) 0.64MI 37 9.56 (9.93) 3.29 (7.05) 6.27 (12.30) 0.62Overall 67 9.53 (10.47) 3.16 (7.11)* 6.37 (12.14) 0.63

Cannabis C 43 6.66 (7.77) 3.29 (4.80) 3.37 (6.99) 0.39MI 35 7.62 (11.14) 2.24 (5.53) 5.38 (10.46) 0.62Overall 78 7.09 (9.38) 2.82 (5.13)* 4.27 (8.72) 0.49

Amphetamines C 9 0.86 (0.91) 0.06 (0.15) 0.80 (0.97) 0.86MI 13 0.66 (0.92) 0.27 (0.90) 0.39 (1.40) 0.42Overall 22 0.74 (0.90) 0.19 (0.75) 0.56 (1.24) 0.59

BSI C 56 1.63 (0.90) 1.23 (0.86) 0.40 (0.75) 0.43MI 56 1.83 (0.93) 1.16 (0.92) 0.67 (0.81) 0.71Overall 112 1.73 (0.92) 1.20 (0.89)** 0.53 (0.79) 0.56

a C: control – assessment only; MI: motivational interview.b Using as a reference point the grand standard deviation for the relevant variable (i.e. across all assessment occasions).† Non-significant trend, MI versus C: P = 0.04.* Overall reduction P < 0.01.** Overall reduction on BSI P < 0.001.



DISCUSSION

The findings of the present study are suggestive of amodest, short-term effect for a MI on an aggregate indexof AOD use among in-patients in psychiatric hospitalwith AOD problems. The differential reduction in meanpolydrug use scores from pre-treatment to 3-monthfollow-up among the MI and control groups (0.93 versus0.42) represents a modest difference in effect size units(0.70 versus 0.32, a ratio of 2.19 : 1), which may be ofa clinically significant magnitude.

The size of change in polydrug use can be comparedto the size of change detected between groups in tworecent studies of behaviour change among people withpsychotic illnesses. Based on a six-session intervention,Kemp and colleagues (Kemp et al. 1996) reported differ-ential improvement at 3-month follow-up among theintervention and control groups in mean treatment com-pliance scores of 2.0 versus 0.4 (or 1.33 versus 0.27 ineffect size units, a ratio of 4.9 : 1). Swanson and col-leagues (Swanson, Pantalon & Cohen 1999) reportedthat one session of motivational interviewing improved

Table 3 OTI, SCID and BSI pre-treatment and follow-up scores by treatment group.

Mean (SD)

3-month 6-month 12-monthVariables Groupa n Pre-treatment follow-up follow-up follow-up

All subjects; continuous variablesSCID: no. of categories for C 50 1.48 (1.02) – 1.16 (1.53) 1.24 (1.29)which abuse or dependence MI 52 1.71 (1.45) – 1.19 (1.27) 0.81 (1.01)criteria were met Overall 102 1.60 (1.25) – 1.18 (1.40) 1.02 (1.17)OTI polydrug use C 46 3.30 (1.23) 2.74 (1.25) 2.52 (1.28) 2.70 (1.15)(out of 11) MI 43 3.23 (1.19) 2.33 (1.15) 2.74 (1.14) 2.63 (1.22)

Overall 89 3.27 (1.20) 2.54 (1.22) 2.63 (1.21) 2.66 (1.18)OTI social functioning C 50 19.16 (5.27) – 17.40 (4.22) 17.30 (4.52)

MI 52 17.79 (6.58) – 16.69 (6.21) 15.88 (5.40)Overall 102 18.46 (5.98) – 17.04 (5.31) 16.58 (5.01)

OTI crime C 50 0.60 (1.39) – 0.36 (0.85) 0.30 (0.93)MI 52 0.23 (0.76) – 0.33 (1.04) 0.23 (0.61)Overall 102 0.41 (1.12) – 0.34 (0.95) 0.26 (0.78)

BSI C 44 1.61 (0.88) 1.18 (0.87) 1.03 (0.80) 1.12 (0.84)MI 43 1.77 (0.98) 1.05 (0.87) 0.92 (0.77) 0.90 (0.86)Overall 87 1.69 (0.93) 1.12 (0.86) 0.97 (0.78) 1.01 (0.85)

Subjects meeting intervention threshold criteria; continuous variablesOTI alcohol C 23 9.56 (12.21) 1.51 (2.05) 4.19 (7.74) 1.83 (3.54)

MI 28 8.24 (7.89) 2.55 (5.29) 4.26 (6.59) 2.98 (3.11)Overall 51 8.84 (9.98) 2.08 (4.15) 4.23 (7.06) 2.46 (3.33)

OTI cannabis C 34 6.21 (7.21) 3.44 (4.69) 3.89 (6.22) 4.47 (6.09)MI 28 8.44 (11.84) 2.52 (6.10) 4.77 (8.00) 5.81 (7.76)Overall 62 7.22 (9.57) 3.02 (5.35) 4.29 (7.03) 5.07 (6.87)

OTI amphetamines C 8 0.95 (0.93) 0.01 (0.03) 0.17 (0.35) 0.03 (0.05)MI 11 0.51 (0.89) 0.32 (1.05) 0.14 (0.31) 0.06 (0.17)Overall 19 0.70 (0.91) 0.19 (0.80) 0.15 (0.32) 0.05 (0.13)

Categorical variables: n (%)SCID alcohol abuse/ C 24 24/24 (100%) – 4/24 (16.7%) 7/24 (29.2%)dependence present MI 28 28/28 (100%) – 14/28 (50.0%) 11/28 (39.3%)

Overall 52 52/52 (100%) – 18/52 (34.6%) 18/52 (34.6%)SCID cannabis abuse/ C 34 34/34 (100%) – 19/34 (55.9%) 22/34 (64.7%)dependence present MI 28 28/28 (100%) – 14/28 (50.0%) 14/28 (50.0%)

Overall 62 62/62 (100%) – 33/62 (53.2%) 36/62 (58.1%)SCID amphetamines abuse/ C 8 8/8 (100%) – 4/8 (50%) 3/8 (37.5%)dependence present MI 11 11/11 (100%) – 4/11 (36.4%) 1/11 (9.1%)

Overall 19 19/19 (100%) – 8/19 (42.1%) 4/19 (21.1%)

a C: control – assessment only; MI: motivational interview.* Significant main effect for time (P < 0.01).† Trend for main effect for time (P = 0.04).



out-patient treatment attendance at the first appoint-ment following hospitalization among 93 psychiatric in-patients with concomitant substance abuse/dependencedisorders. While 42% of motivational interview subjectsattended their first out-patient appointment, only 16% ofstandard treatment patients attended (a ratio of 2.6 : 1).In a recent study of substance users, Donovan and colleagues (Donovan et al. 2001) reported that a pre-treatment motivational interview aimed to prevent attrition did not impact on treatment attendance or abstinence from illicit drug use (ratio 0.92 : 1) comparedwith standard care.

It appears that the difference in effect size between theMI and control conditions in the present study is similarto that found between the one-session motivational inter-view and standard treatment by Swanson and colleagues(Swanson et al. 1999). The six-session intervention byKemp and colleagues was associated with a compara-tively larger effect size. Thus, the intervention effect mayhave been stronger in the present study if the interven-tion was longer than a single session. Also, the changewas evident only on an aggregate measure that combinedreductions in substances across drug types. Thus, to theextent that the intervention had any effect, it was adiffuse effect. Further, these results should be interpretedwith caution as urinalyses were not conducted and ther-apist effectiveness was not explored. The effect was notmaintained longer than 3 months. Several motivationalintervention sessions with people while they remain in-patients, and further follow-up in the community withcognitive-behaviour therapy aimed at preventing relapsemay be more effective.

One possible reason for the longer-term ineffective-ness of the MI on AOD use is the severity and chronicityof the substance use problems and mental illness amongthe sample. As brief interventions are more effectiveamong people with lower levels of dependence (Mattick& Jarvis 1993) and among non-treatment seekers (albeitfor AOD problems) (Heather 1995), the present resultsare consistent with previous research.

Conducting the present study within a service contextmay have set constraints on the power to detect inter-vention effects for specific substances. There was mostpower to detect an intervention effect for cannabis (n = 43versus 35 at pre-treatment and 3 months). With samplesizes such as this, one would need to anticipate popula-tion effect sizes of three-quarters of a standard deviationto have adequate power (80%) to detect group differencesat the P < 0.01 level. Thus, future randomized controlledtrials should either target samples of users of particularsubstance classes or employ very large samples.

The scope and size of the study did not allow foranalyses of all the possible variables that may haveimpacted on outcome (e.g. current type of psychiatric

treatment, assertiveness of follow-up, access to other ser-vices, AOD use patterns). These factors should be investi-gated in future studies.

The sample as a whole improved significantly overtime on several variables: the number of SCID categoriesfor which abuse or dependence criteria were met; OTIsocial functioning; symptomatology; and OTI alcoholconsumption scores among subjects meeting thresholdcriteria. Variables associated with improvement need tobe identified and incorporated into future treatmentswhere possible. It may be that the lengthy assessmentreceived in the course of this study and the in-patientadmission resulted in a degree of behaviour change thatmade it difficult to detect an intervention effect for the MI.

On the other hand, cannabis use did not show a sus-tained reduction over time among subjects meeting inter-vention threshold criteria at pre-treatment. At 12-monthfollow-up the average number of joints or bongs smokedper day was just over five. Intervention criteria at pre-treatment and 12-month follow-up, respectively, weremet by 60.6% and 33.0% of the sample for alcohol,66.3% and 52.2% for cannabis, and 22.5% and 12.2%for amphetamines. Thus, while the alcohol and amphet-amine intervention threshold was met by virtually halfof the previous proportion at 12 months, the majority ofcannabis users continued to use at levels requiring inter-vention. This implies that while alcohol and ampheta-mine may be used at times of high stress preceding ahospital admission, cannabis use is influenced less by sit-uational crises and is more constant in people’s lives. Itappears that cannabis use should be addressed specifi-cally during in-patient admissions. It is intriguing thatBSI scores improved over time despite relatively highlevels of cannabis use among the sample. This findingimplies that cannabis use may not necessarily impactupon psychiatric symptomatology. Interventions mayneed to focus on the health and other costs associatedwith the illicit nature of the drug, such as having toengage in crime to finance use of the drug, as indicatedby the present results.

The finding that precontemplators reported moresevere symptomatology implies that interventions withprecontemplators should focus on strengthening under-standing of the possible association between AOD useand symptomatology. Conversely, others who are lesssymptomatic may be more conscious of the need toadjust their use of AOD to avoid exacerbation ofsymptoms.

The main conclusion from the present study is that a brief motivational intervention appeared to have amodest effect on polydrug use in the short term amongin-patients with AOD problems. A substantial proportionof subjects was still above our intervention threshold atthe 12-month follow-up, particularly for cannabis. In a



previous paper (Baker et al. 2002) the MI did not enhanceengagement in a SSMS. Together, these results suggestthat we need to: (i) ascertain the particular client char-acteristics that best predict good outcome with briefinterventions; and (ii) evaluate longer interventions,which commence during the in-patient period and con-tinue following discharge from hospital.

ACKNOWLEDGEMENTS

This work was funded by a Research into Drug AbuseGrant (RIDAG) from the Commonwealth Department ofHealth and Aged Care. Natalia Carter assisted in pilotingthe study, funded by a Research Management CommitteeGrant from the University of Newcastle. We wish tothank the study participants and the ward and medicalrecord department staff of the hospital from which par-ticipants were recruited.

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Evaluation of a motivational interview for substance use within psychiatric in-patient services

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