1 Medical University of Luebeck, Department of Psychiatry and Psychotherapy, Research Group S:TEP (Substance Abuse: Treatment, Epidemiology and Prevention), Luebeck, Federal Republic of Germany and 2 Ernst-Moritz Arndt University, Department of Epidemiology and Prevention, Greifswald, Federal Republic of Germany
* Author to whom correspondence should be addressed at: Universitätsklinikum Schleswig-Holstein, Campus Lübeck, Klinik für Psychiatrie und Psychotherapie, Ratzeburger Allee 160, 23538 Lübeck, Germany. Tel.: +49 451 5004813; Fax: +49 451 5003480; E-mail: Janina.Grothues{at}ukl.mu-luebeck.de
(First received 8 October 2004; first review notified 20 January 2005; final revised form 18 May 2005; accepted 10 June 2005)
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ABSTRACT |
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INTRODUCTION |
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The Transtheoretical Model (TTM) (Prochaska and DiClemente, 1984, 1986
, 1992
, Prochaska et al., 1992
) provides an excellent framework for studying such relations. It postulates that behaviour alteration requires individuals to systematically proceed through five motivational stages. During the precontemplation stage of change, individuals are either unconvinced that behaviour change is necessary, or are unwilling to consider change. In the contemplation stage, individuals consider the possibility of change by weighing its costs against its benefits. In the preparation stage, individuals commit to change and undertake initial planning of how to pursue it, while in the action stage, concrete plans are put into practice. During the maintenance stage, individuals consolidate the alterations made and integrate them into their lifestyles. Differential use of cognitive-behavioural processes leads to higher readiness and more consistent change. During the early stages, such mechanisms are of experiential nature, e.g. consciousness raising and social re-evaluation. From the preparation stage onwards, behavioural processes, such as counter-conditioning and stimulus control, become central. Decisional balancing, a weighing of the positive and negative aspects of drinking, can be usefully allied with the cognitive shifts across the stages and the use of experiential and behavioural processes (DiClemente et al., 1985
). The TTM suggests, that personal discomfort, namely if the costs of drinking outweigh the benefits, may lead to behaviour change. Previous research suggests, that the more discouraged and frustrated with their alcohol use individuals become, the less ambivalence they experience and the more willing they become to take action to address that problem (Isenhart and Van Krevelen, 1998
). Self-efficacy evaluates both the individual's level of temptation to drink when faced with various internal and situational cues, and the person's confidence in his or her own abilities to abstain from drinking in these situations. Previous studies using the TTM have found that mechanisms, which facilitate change and buffer a person from relapse, are the following: higher readiness to change and greater use of the respective experiential and behavioural change processes, higher rating of the negative aspects of drinking while rating the positives lower, lower temptation to drink and higher confidence in one's own abilities to abstain from drinking (Prochaska and DiClemente, 1992
; Project MATCH Research Group, 1998
).
Previously, one study had looked at the association between TTM variables and severity of drinking in the dually diagnosed (Velasquez et al., 1999). The authors found a positive correlation between psychiatric severity as measured on nine subscales of a brief symptom inventory and the maintenance stage of change in an outpatient dual diagnoses sample. Psychiatric severity was positively correlated with the negative aspects of drinking and temptation to drink, particularly in situations that triggered negative effects. In order to gain insights on drinking behavioural change in individuals with depression and anxiety, and who do not seek help, three aspects need to be addressed: First, previous focus on clinical populations implies reactive sampling, which supposedly involves higher motivation to change at baseline than might be found in pro-actively recruited individuals. Second, exploration is needed, on how far prior findings on readiness to change in alcohol-dependent samples apply to at-risk and binge drinking populations. Third, previous findings on TTM and comorbidity are largely based on symptomatology of psychiatric distress rather than standardised diagnostic measures according to DSM-IV. The chief objective of this paper is to provide data on the interaction between comorbid anxiety or depression and readiness to change drinking behaviour in a sample of pro-actively recruited individuals with a range of drinking problems, and who do not seek treatment for their drinking or mental health problems.
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METHODS |
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To minimise time for data collection within the practice, the procedure was threefold: screening within the practice, sending postal questionnaires, and administering telephone diagnostic assessments outside the practice. The time schedule of assessments is shown in Table 1.
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Instruments
Screening within the practice. The Alcohol Use Disorder Identification Test (AUDIT) (Saunders et al., 1993), a 10-item self-report questionnaire that identifies at-risk drinking or problem drinking which is broader than abuse or dependence as well as personal and social harm reflective of drinking, was used for the initial screening. Based on data of a German general population sample (Rumpf et al., 2002
), a cut-off value of five points was chosen. Additionally, the Luebeck Alcohol dependence and abuse Screening Test (LAST) (Rumpf et al., 1997
) indicated positive screening of alcohol abuse or dependence at a cut-off value of two points. Positive screening on either the AUDIT or the LAST indicated eligibility for further study participation.
Diagnostic measures via telephone assessment. The 12-month version of the Munich Composite International Diagnostic Interview (M-CIDI) (Wittchen et al., 1995), which is the German translated version of the WHO-CIDI (Robins et al., 1988
) but is otherwise identical, was used for diagnostic identification of alcohol abuse or dependence according to the fourth and international version of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1995
). Further inclusion criteria were at-risk drinking, defined as an average consumption of >20/30 grams of alcohol per day for men/women within the last 4 weeks (British Medical Association, 1995
) and/or criteria of binge drinking, defined as >60/80 grams of alcohol for women/men on at least two occasions within the last four weeks (Babor et al., 1992
).
For diagnostic purposes of mental disorders in conjunction with the definitions and diagnostic criteria of the Diagnostic and Statistical Manual of psychiatric disorders (DSM-IV), the diagnostic sections of the 12-month version of the M-CIDI included the following groups: major depressive disorder, dysthymic disorder, panic disorder with and without agoraphobia, agoraphobia without history of panic disorder, social phobia, generalised anxiety disorder, and anxiety disorder not otherwise specified.
Measures of the TTM and alcohol related problems via postal questionnaire. The German 12-item version of the Readiness to Change Questionnaire (RCQ-G) (Hannöver et al., 2001a) was used to assess participants' readiness to change. Internal consistency and construct validity of the RCQ-G have been shown to be satisfactory on assessment in a German general population sample (Hannöver et al., 2001a
). Further information on the predictive validity of the instrument may be found in Heather et al. (1993)
. Stages of change were allocated using the quick method (Heather et al., 1993
), which assesses three stages of change (precontemplation, contemplation, and action) according to the highest subscale score. The refined method of allocation, which analyses the relationship of positive and negative scale scores as a profile of three scores, was rejected as it results in a certain proportion of cases that cannot be allocated (Hannöver, 2002
).
The German 40-item version of the Processes of Change Questionnaire-Alcohol (POC-A) (DiClemente et al., 1996; Freyer et al., 2003
) was administered to measure experiential and behavioural processes of change as classified by the TTM. Four items each are grouped to represent ten processes. Higher sum scores of the ten processes reveal more frequent use.
Participants' perceived pros and cons of drinking (13 items each) were estimated by the adapted German translation of the Alcohol Decisional Balance Scale (ADBS) (Hannöver et al., 2001b; King and DiClemente, 1993
). Each scale is derived from adding the respective item scores. Higher scale values indicate higher relevance of pros or cons of drinking.
The 20-item German version of the Alcohol Abstinence Self Efficacy Scale (AASE) (Bott et al., 2003; DiClemente et al., 1994
) was used to measure temptation to drink in relation to different situational and emotional states and individuals' self-efficacy to abstain from drinking when confronted with these situations. By adding the item scores, an overall temptation/self efficacy score is built. Higher values represent higher temptation/self-efficacy.
Adverse consequences from drinking (ACD) were assessed using nine items (e.g. problems with your job, family arguments) of the Health and Daily Living Form (HDL) Moos, Cronkite and Finney, (1990). The scale provides a measure of psychosocial problems connected with drinking. A sum score represents the amount of adverse consequences of drinking.
Participants
In total, 10 803 patients were screened. Among these, 2475 averred not consuming alcohol at all. Of the remaining 8328 screenings, 2239 (26.9%) were positive on the AUDIT and/or the LAST. Of these, 1410 patients subsequently agreed to participate in the study (response rate 63.0%). Later, 7% of these withdrew further participation and 13.6% had to be excluded for other reasons (e.g. no telephone or mail access). Telephone diagnostic interviews could be conducted with 1119 patients (79, 4% of all positively screened patients with informed consent). Among these, 645 patients (57.6%) did not fulfil diagnostic criteria for alcohol use disorders or problematic drinking. The return of the postal questionnaire could not be obtained from 66 patients. The final study sample included 408 participants on grounds of alcohol dependence, abuse, at-risk drinking or binge drinking. Of these, 278 participants (68.1%) were male and 130 (31.9%) were female. The mean age was 36.9 (SD = 13.44; range 1864).
Analysis Procedures
Groups 1 (alcohol use disorder only) and 2 (comorbid anxiety and/or depression) were compared using chi-square, t-tests and MannWhitney U-tests. Multinomial logistic regression analysis with stages of change as the dependent variable (reference category: action) was used as a multivariate approach to predict readiness to change. ACD and comorbidity were used as predictors (independent variables). Results are shown as odds ratios and confidence intervals.
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RESULTS |
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Psychiatric comorbidity
Of the final study sample, 320 participants (78.4%) did not meet diagnostic comorbidity criteria, while 88 participants (21.6%) were diagnosed with comorbid anxiety and/or depressive disorder. Of these, 35 participants were diagnosed with comorbid depression only, 30 with comorbid anxiety only, and 23 participants with both comorbid anxiety and depressive disorder. Compared to non-comorbid patients, comorbid participants were significantly more often alcohol dependent as opposed to alcohol abusers, at-risk drinkers and binge drinkers (chi-squared = 42.1; df = 3; P < 0.001). They were significantly more often female (chi-squared = 17.0; df = 1; P < 0.001) and did not differ from non-comorbid individuals in years of schooling (up to 9 years versus >9 years; chi-squared = 1.6; df = 1; P = 0.21) and age (t = 1.5; df = 152.2; P = 0.14).
Transtheoretical model variables and psychiatric comorbidity
Psychiatric comorbidity was significantly related to readiness-to-change drinking (chi-squared = 27.2; df = 2; P < 0.001). On grounds of analysis including all classifications of problematic drinking (dependence, abuse, at-risk, and binge-dinking), comorbid individuals were significantly more often represented in the contemplation stage, whereas non-comorbid individuals were significantly more often represented in precontemplation. The same trend remained for differential analyses of the stages of change distribution within each classification of problematic drinking. However, significance was only obtained for alcohol abuse (chi-squared = 8.6; df = 2; P < 0.01). Results are presented in Table 2.
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DISCUSSION |
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Some of the findings by the Velasquez et al. (1999) study, who found a positive correlation between psychiatric severity and higher stages of change, with the cons of drinking, and with the temptation to drink in psychiatric outpatients could be confirmed by our data, using categorical diagnoses from a pro-actively recruited sample. Additionally, our study provides information on the relationship between stages of change and the different categories of problematic drinking or psychiatric comorbidity, as well as further insight into decisional balancing and self-efficacy.
Analyses comparing individuals with either psychiatric disorder to participants without comorbidity showed that stages of change differences were significant for both groups, but more profound for anxiety. In all subgroups of alcohol use disorders and problematic drinking, readiness to change was elevated for comorbid individuals; however, significance was only found for alcohol abuse. This finding suggests that the negative consequences from drinking abusers have experienced, might interact with the comorbid disorder and lead to a more pronounced cognitive evaluation process. The special status of abuse as opposed to the other categories might be explained by the fact that the negative consequences from drinking are more apparent in this category than in others, where at least part of the alcohol dependents or at-risk drinkers may not currently experience negative consequences or may not attribute them to their alcohol consumption. In order to examine, if either comorbidity or ACD were the better predictor for readiness to change, multinomial logistic regression analysis showed a three times elevated chance for comorbid individuals to be in action (reference category) as opposed to precontemplation, when only comorbidity was used as an independent variable. However, when ACD was additionally entered, only these became significant, while comorbidity lost its predictive value. Hence, data indicate that personal discomfort from drinking predicts readiness to change better than comorbidity does, when both factors are considered.
The TTM suggests that personal discomfort, namely, if the costs of drinking outweigh the benefits, may lead to behavioural change. In addition to the previous clinical findings (Velasquez et al., 1999), comorbid individuals of our pro-actively recruited sample did not only rate the negative aspects of drinking higher, but also the positives. On the one hand, this shows a generally stronger evaluation process compared to non-comorbid participants, but on the other hand may indicate prolonged contemplation before a decision to change can be reached. The use of cognitive and behavioural processes of change were higher for comorbid individuals on all subscales, suggesting that comorbid individuals are more concerned about their drinking and so search for appropriate coping strategies. This fits in with the higher stages of change. However, comorbid individuals were also more strongly tempted to drink than non-comorbid participants. In addition to the Velasquez et al. (1999)
study, our findings show comorbid individuals to be less confident in abstaining from drinking in a variety of situations. Results clearly have implications for intervention strategy. While comorbid individuals seem to be well accessible for interventions aimed at motivational enhancement to reduce problematic drinking, treatment planning ought to focus on shifting decisional balancing towards the negative aspects of drinking, and on raising self-efficacy (Prochaska and DiClemente, 1992
) while strengthening alternative ways of coping with tempting situations.
Some limitations of our study have to be taken into account: The assessment procedure was designed to take up the least time necessary within the practice setting, therefore supplementary assessments were done via mail and telephone. However, the possible bias related to this procedure is likely to be marginal. The use of the RCQ in our study might be a source of concern, since this questionnaire has been criticised: using the quick method overestimates readiness, while using the refined method leads to a substantial proportion of individuals who cannot be allocated (Hannöver et al., 2002). Other instruments like the University of Rhode Island Change Assessment Scale (URICA) (DiClemente and Hughes, 1990
) would be more precise. However, the RCQ was chosen owing to its brevity and comparability with previous studies in primary care settings. Alternative strategies for analysing stages of change scales like the RCQ, as proposed by DiClemente et al. (2004)
, could be promising, although comparability with other studies using the RCQ would no longer be given. The impact on the data when using the RCQ and the quick method is deemed to be rather small, since the possible overestimation of readiness is true for all groups and is unlikely to alter the differences between groups.
In sum, findings show comorbidity to be a crucial aspect to be considered in pro-actively designed brief intervention treatment. Our study is limited by its cross-sectional design. Future studies could profit from longitudinal data.
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ACKNOWLEDGEMENTS |
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REFERENCES |
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![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Babor, T. F., Hodgson, B., Ritson, B., McRee, G., Ernberg, K., Connor, K. and Grant, M. (1992) Experimental design and project administration. In Programm on Substance Abuse. Project on identification and management of alcohol-related problems. Report on Phase II: A Randomized Clinical Trial of Brief Interventions in Primary Health Care, Babor, T. F. and Grant, M. eds, pp. 1556. World Health Organization, Geneva.
Bijl, R. V., Ravelli, A. and van Zessen, G. (1998) Prevalence of psychiatric disorder in the general population: results of the Netherlands Mental Health Survey and Incidence Study (NEMESIS). Social Psychiatry and Psychiatric Epidemiology 33, 587595.[CrossRef][ISI][Medline]
Bischof, G., Reinhardt, S., Grothues, J. et al. Effect of item sequence on the performance of the AUDIT in general practices. Drug and Alcohol Dependence, in press.
Bott, K. E., Rumpf, H. J., Bischof, G., Meyer, C., Hannöver, W., Hapke, U. and John, U. (2003) Alkoholabstinenz-Selbstwirksamkeitsfragebogen; deutsche Version (AASE-G): Deutsche Version der Alcohol Abstinence Self-Efficacy (AASE) Scale [Alcohol Abstinence Self-Efficacy-Scale, German Version]. In Elektronisches Handbuch zu Erhebungsinstrumenten im Suchtbereich (EHES)[Electronic Handbook on Assessment Instruments in the Addiction Field], Vol. 3.00, A. Glöckner-Rist, F. R. and H. Küfner ed. Zentrum für Umfragen, Methoden und Analysen. [Available on line: www.psy.unimuenster.de/institut1/ehes/startseite.htm.], Mannheim.
British Medical Association (1995) Guidelines on sensible drinking. British Medical Association, London.
DiClemente, C., Schlundt, D. and Gemmell, L. (2004) Readiness and stages of change in addiction treatment. American Journal on Addictions 13, 103119.[CrossRef][ISI][Medline]
DiClemente, C. C., Carbonari, J. P., Addy, R. C. and Velasquez, M. M. (1996) Alernate short forms of a process of change scale for alcoholism treatment. Paper presented at the Fourth International Congress on Behavioral Medicine, 1996.
DiClemente, C. C., Carbonari, J. P., Montgomery, R. P. G et al. (1994) The alcohol abstinence self-efficacy scale. Journal of Studies on Alcohol 55, 141148.[ISI][Medline]
DiClemente, C. C. and Hughes, S. O. (1990) Stages of change profiles in outpatient alcoholism treatment. Journal of Substance Abuse 2, 217235.[Medline]
DiClemente, C. C., Prochaska, J. O. and Gibertini, M. (1985) Self-efficacy and the stages of self-change of smoking. Cognitive Therapy and Research 9, 181200.[CrossRef][ISI]
Freyer, J., Schumann, A., Rumpf, H. J., Meyer, C., Hapke, U. and John, U. eds, (2003) Deutsche Version der Processes of Change Scale für Alkoholkonsumenten (POC-A) [German version of the Processes of Change Scale for alcohol consumption]. Zentrum für Umfragen, Methoden und Analysen Available on line: www.psy.uni-muenster.de/institut1/ehes/startseite.htm., Mannheim.
Grant, B. F. (1997) Barriers to alcoholism treatment: reasons for not seeking treatment in a general population sample. Journal of Studies on Alcohol 58, 365371.[ISI][Medline]
Grant, B. F. and Harford, T. C. (1995) Comorbidity between DSM-IV alcohol use disorders and major depression: results of a national survey. Drug and alcohol dependence 39, 197206.[CrossRef][ISI][Medline]
Greenley, J., Mechanic, D. and Cleary, P. (1987) Seeking help for psychological problems. A replication and extension. Medical Care 25.
Hannöver, W., Rumpf, H.-J., Meyer, C., Hapke, U. and John, U. (2001a) Der Fragebogen zur Änderungsbereitschaft bei Alkoholkonsum (RCQ-D). In Elektronisches Handbuch zu Erhebungsinstrumenten im Suchtbereich (EHES). Version 1.00, Glöckner-Rist, A., Rist, F. and Küfner, H. eds. Zentrum für Umfragen, Methoden und Analysen, Mannheim.
Hannöver, W., Rumpf, H.-J., Meyer, C., Hapke, U. and John, U. (2001b) Die Skala zur Entscheidungsbalance bei Alkoholkonsum (ADBS-D). In Elektronisches Handbuch zu Erhebungsinstrumenten im Suchtbereich (EHES). Version 1.00, Küfner, H. ed. Zentrum für Umfragen, Methoden und Analysen, Mannheim.
Hannöver, W., Thyrian, J. R., Hapke, U. et al. (2002) The readiness to change questionnaire (RCQ) in subjects with hazardous alcohol consumption, alcohol misuse and dependence in a general population survey. Alcohol and Alcoholism 37, 362369.
Hasin, D., Liu, X., Nunes, E. et al. (2002) Effects of major depression on remission and relapse of substance dependence. Archives of General Psychiatry 59, 375380.
Heather, N., Rollnick, S. and Bell, A. (1993) Predictive validity of the readiness to change questionnaire. Addiction 88, 16671677.[ISI][Medline]
Isenhart, C. E. and Van Krevelen, S. (1998) Relationship between readiness for and processes of change in a sample of alcohol dependent males. Journal of Substance Abuse 10, 175184.[CrossRef][ISI][Medline]
Kessler, R. C., Crum, R. M., Warner, L. A. et al. (1997) Lifetime co-occurrence of DSM-III-R alcohol abuse and dependence with other psychiatric disorders in the National Comorbidity Survey. Archives of General Psychiatry 54, 313321.[Abstract]
King, T. K. and DiClemente, C. C. (1993) A decisional balance measure for assessing and predicting drinking behavior. University of Houston, TX, USA.
Modesto-Lowe, V. and Kranzler, H. R. (1999) Diagnosis and treatment of alcohol-dependent patients with comorbid psychiatric disorders. Alcohol Research and Health 23, 144149.[ISI][Medline]
Prochaska, J. O. and DiClemente, C. C. (1984) The transtheoretical approach: crossing traditional boundaries of therapy. Dow Jones Irwin, Homewood, IL.
Prochaska, J. O. and DiClemente, C. C. (1986) Toward a comprehensive model of change. In Treating Addictive Behaviors: Processes of Change, Miller, W. R. and Heather, N. eds, pp. 327, Plenum Press, New York.
Prochaska, J. O. and DiClemente, C. C. (1992) Stages of change in the modification of addictive behaviors. In Progress in Behavior Modification, Vol. 28, Hersen, M., Eisler, R. M. and Miller, P. M. eds, pp. 367. Sycamore Publishing Company, Pittsburgh.
Prochaska, J. O., DiClemente, C. C. and Norcross, J. C. (1992) In search of how people change. American Psychologist 47, 11021114.[CrossRef][ISI][Medline]
Project Match Research Group (1998) Matching alcoholism treatments to client heterogeneity: treatment main effects on drinking during treatment. Journal of Studies on Alcohol 59, 631639.[ISI][Medline]
Regier, D. A., Farmer, M. E., Rae, D. S. et al. (1990) Comorbidity of mental disorders with alcohol and other drug abuse: results from the epidemiologic catchment area (ECA) Study. Journal of American Medical Association 264, 25112518.[Abstract]
Rickwood, D. and Braithwaite, V. (1994) Social-psychological factors affecting help-seeking for emotional problems. Social Science in Medicine 39, 563572.[CrossRef]
Robins, L. N., Wing, J. and Wittchen, H. U. (1988) The Composite International Diagnostic Interview: an epidemiological instrument suitable for use in conjunction with different diagnostic systems and in different cultures. Archives of General Psychiatry 45, 10691077.[Abstract]
Rumpf, H.-J., Hapke, U., Hill, A. et al. (1997) Development of a screening questionnaire for the general hospital and general practices. Alcoholism: Clinical and Experimental Research 21, 894898.[ISI][Medline]
Rumpf, H.-J., Hapke, U., Meyer, C. et al. (1999) Motivation to change drinking behavior: comparison of alcohol dependent individuals in a general hospital and a general population sample. General Hospital Psychiatry 21, 348353.[CrossRef][ISI][Medline]
Rumpf, H.-J., Hapke, U., Meyer, C. et al. (2002) Screening for alcohol use disorders and at-risk drinking in the general population: psychometric performance of three questionnaires. Alcohol and Alcoholism 37, 261268.
Saunders, J. B., Aasland, O. G., Babor, T. F. et al. (1993) Development of the Alcohol Use Disorders Identification Test (AUDIT): WHO collaborative project on early detection of persons with harmful alcohol consumption-II. Addiction 88, 617629.
Schuckitt, M. A. (1996) Alcohol, anxiety and depressive disorders. Alcohol Health and Research World 20, 739745.
Velasquez, M. M., Carbonari, J. P. and DiClemente, C. C. (1999) Psychiatric severity and behavior change in alcoholism: the relation of the transtheoretical model variables to psychiatric distress in dually diagnosed patients. Addictive Behaviors 24, 481496.[CrossRef][ISI][Medline]
Wittchen, H.-U., Beloch, E., Garczynski, E., Holly, A., Lachner, G., Perkonigg, A., Vodermaier, A., Vossen, A., Wunderlich, U. and Zieglgänsberger, S. (1995) Münchener Composite International Diagnostic Interview (M-CIDI), Version 2.2. Max-Planck-Institut für Psychiatrie, München.
Wittchen, H.-U., Essau, C. A., Zerssen, D. V. et al. (1992) Lifetime and six-month prevalence of mental disorders in the Munich Follow-Up Study. European Archives of Psychiatry and Clinical Neuroscience 241, 247258.[ISI][Medline]
Wittchen, H.-U., Perkonigg, A. and Reed, V. (1996) Comorbidity of mental disorders and substance use disorders. European Addiction Research 2, 3647.
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