It is common clinical experience that outcomes for people suffering from schizophrenia and SUD are unfavorable, particularly when patients are treated sequentially or in parallel, but in separate settings for the two disorders. This is probably related to fundamental differences in the philosophies of psychiatric and addiction care services, which often result in strict exclusions and low tolerance for symptoms from the “other” disorder in many traditional treatment settings. These problems contribute to the low compliance of patients who thus fall “between the cracks.”

By now, the dominant view amongst experts favors integrated treatment approaches delivered by multidisciplinary teams of therapists who are experienced and competent in the treatment of both schizophrenia and SUD. The integrated treatment approach should adapt and balance supportive elements of psychiatric care with elements from addiction therapies which tend to rely on patients assuming responsibility for themselves. Beginning in the late 1990s integrated treatment programs were developed and implemented in the USA and in several European countries such as the UK (Lowe and Abou-Saleh 2004), Switzerland (Moggi et al. 2002), and Belgium (Morrens et al. 2011). Several reports from model projects and over 50 controlled and quasiexperimental studies showed better long-term outcomes particularly for low-threshold, long-term outpatient therapeutic programs (Drake and Mueser 2000; Drake et al. 2004, 2008; De Witte et al. 2013). Such programs with out-reaching components do not require absolute abstinence; rather they aim at low patient attrition and strengthening of patient motivation to reduce substance use.

All programs with relatively favorable long-term outcomes combine pharmacotherapy, psychoeducation, and motivational approaches. In addition, some programs offer cognitive behavioral therapies and family interventions and some cooperate with self-help groups for dually diagnosed patients (double trouble (DT) groups).

Motivational Interviewing (MI) is a core component of treatments for addictive disorders. For people with comorbid schizophrenia, interview techniques have to be modified and adapted in order to account for the common cognitive deficits of this population [MBDDT: Motivation-Based Dual Diagnosis Treatment (Drake and Mueser 2000)]. MI and psychoeducation are core interventions for the majority of patients who are in low motivational states. Even short motivational interventions consisting of four, three, or even a single session were shown to be effective in terms of higher utilization of further treatment offers (Gouzoulis-Mayfrank 2007; Bechdolf et al. 2012). However, motivational interventions alone are rarely sufficient to reduce substance use.

Psychoeducation is the second corner stone of psychosocial therapies for people with schizophrenia and SUD. Patients have to be informed about the interrelations between psychosis and substance use, about the interaction between drug effects and the individual vulnerability for psychosis and about the negative impact of drug use, particularly cannabis, on the course of psychosis. Effective psychoeducation may serve to build and enhance motivation to stop or at least reduce substance use. To date, there are two published German language manuals for group psychoeducation for dual disorder patients (Komorbidität Psychose und Abhängigkeit, KomPAkt, Gouzoulis-Mayfrank 2007; Gesund und Ohne Abhängigkeit Leben, GOAL, D’Amelio and Behrendt 2007).

Cognitive behavioral therapies are indicated for patients in higher motivational states. Nevertheless, it is important to take into account the limited cognitive resources of patients with schizophrenia in terms of concentration and abstraction abilities. In Dual Diagnosis Relapse Prevention Therapy (DDRP, Ziedonis and D’Avanzo 1998) specific abstinence-related skills such as recognition and avoidance of risk situations and resistance skills are combined with general social skills such as communication skills and assertiveness. In Behavioral Treatment of Substance Abuse in Schizophrenia (BTSAS, Bennett et al. 2001) patients are trained in general social skills ahead of abstinence related skills and problem solving. The German language program Komorbidität Psychose und Abhängigkeit Skills Training (KomPASs, Gouzoulis-Mayfrank 2007) adds cognitive techniques to the training range focusing on cognitions, behaviors, and risk situations relevant for both psychosis and SUD.

Finally, family interventions use cognitive behavioral techniques and psychoeducation. Key focus areas are the interrelations between psychosis and substance use and a broadening of the biological concept of psychosis so as to include SUD. Communication training aims to blunt emotional dynamics in the family and reduce high expressed emotion, which presents risks for relapse and long-term outcomes of patients. Family Intervention for Dual Disorders (FIDD, Mueser and Fox 2002) includes both psychoeducation and communication training. The German language program Gesund und Ohne Abhängigkeit Leben (GOAL, D’Amelio and Behrendt 2007) concentrates on psychoeducation.

The treatment of patients with schizophrenia and SUD is difficult. Subject to realistic targets and a long-term treatment plan, positive outcomes are nevertheless possible. By now, there is a plethora of controlled experimental or quasiexperimental studies in different settings.

Drake and coworkers published the first qualitative reviews of the literature in 1998, followed by subsequent reviews in 2004 and 2008. The more recent review analyzed 45 randomized and nonrandomized controlled studies with samples between 25 and several hundred patients (Drake et al. 2008). Control groups received standard, non-integrated treatment (TAU) with follow-up up to several months after termination of treatment. In summary, intensive residential programs with strict abstinence requirements and lasting up to 6 months resulted in high drop-out rates of 45–85 % and high relapse rates of up to 95 % within a few months of termination of treatment. In contrast, low threshold, long-term, motivation-based out-patient programs delivered the best results in cost–benefit terms; drop-out rates were below 25 % and roughly half the patients achieved a gradual reduction of substance use accompanied by stabilization of their psychosis and reduction in the frequency of emergency admissions. Studies on the most severely affected homeless patients showed over the 1–3 years course of their treatment a reduction in medical complications related to substance use and improvements in their general medical condition and their social adjustment. However, despite these encouraging results, about half the dually diagnosed patients made only limited progress and about a quarter did not benefit at all from integrated out-patient treatment (“Nonresponder”) (Drake et al. 2008).

Similarly, a recent review of 14 RCTs on integrated treatment programs for dually diagnosed outpatients reported some advantages of the integrated treatment approach; however, effect sizes were mostly modest (De Witte et al. 2013). The authors claimed that more homogeneous and qualitative sound studies are needed. In addition, a Cochrane analysis of 25 RCTs carried out in different settings, failed to demonstrate an overall superiority of integrated programs compared to other treatments, although some studies did show advantages over the control conditions (Cleary et al. 2010). Cleary et al. (2010) also claimed that studies were too heterogeneous. Drake et al. (2008) suggested that some nonresponders may benefit from more intensive residential treatments incorporating elements of the anglosaxon therapeutic communities (“stepped care”). In their most recent literature review, they found that in those cases better results were achieved through longer treatments of at least a year compared to shorter treatments of 6 months or less (Drake et al. 2008).