[Motivational interviewing for patients with comorbid schizophrenia and substance abuse disorders: a review].

Patients with schizophrenia and substance abuse disorders [dually diagnosed patients (DD)] show an unfavourable course of the illness and little interest in participating on specific integrated treatment programmes. Motivational interviewing (MI) has been shown to be effective among other substance abuse disorders and it aims to enhance intrinsic motivation to change problem behaviour. MI has been adapted for DD. The present paper reviews the empirical evidence for the efficacy of MI in DD. A search in the databases MEDLINE, EMBASE, PsycINFO was conducted and the methodological quality of the identified trials was assessed according to the Cochrane Collaboration and to the JADAD Scale. We identified 4 randomised studies with a total of 346 participants, in which MI interventions of 1 to 3 sessions were compared with various control conditions over a follow-up period of up to 6 months. With regard to the main outcome measures "subsequent participation at integrated treatment programme" (1 x positive, 2 x negative) and "substance use" (1 x positive, 1 x negative,) the studies gained contradictory results. In all 4 studies, there were relevant general methodological limitations (randomisation, blindness of raters, description of the reasons for drop-outs) and specific methodological shortcomings (sample size and sample homogenity, numbers of MI sessions, assessment of motivational status). Hence, at present the evidence for supporting MI in DD is not clear. This may be due to the methodological problems mentioned above or it may be that there is, in fact, no effect. Therefore, there is an urgent need for further research of MI in DD.