Clinical trial design in schizophrenia: implications for clinical decisions

PURPOSE OF REVIEW: Results from clinical trials do not necessarily provide information for decisions in clinical practice. This review aims to present strengths and limitations of different methodological types of clinical trials and to offer an overview of how knowledge from clinical trails can be distilled for clinical practice. Selected key questions in the treatment of schizophrenia are presented, with a focus on the possibilities and restrictions of translating trial results into real-world practice. RECENT FINDINGS: Randomized controlled trials are the gold standard for proving efficacy of a diagnostic or therapeutic procedure. They have a high degree of internal validity and a clear-cut message when conducted to good-quality standards but suffer from a lack of generalizability (external validity). Effectiveness studies evaluate effects of treatments under conditions approximating usual care. They may include patient-centred outcomes or health economic evaluations. According to the type of trial, specific problems arise in the interpretation of results. Typical examples are given for the treatment of acute exacerbations of schizophrenia, for relapse prevention and for the treatment of cognitive impairment. SUMMARY: Clinical decisions have to be made upon the best knowledge. Therefore, well conducted studies addressing all major issues from all relevant perspectives are needed. The assessment of a treatment regimen for clinical utility requires both efficacy and effectiveness studies. An understanding of the design, analysis and conventions of both study types is essential for the interpretation of results and their translation to the clinical decision-making process.