The Effectivenessof Mentalhealthcase Management

Declaration of interest None. The search for evidence of the effectiveness of interventions in medicine and the health sciences has a history dating back to the middle ages (Lancaster, 1994). Following the work of Fisher (1935) in theorising the design of the randomised controlled trial (RCT) as the most important method for establishing causality of interventions, RCTs have become widely used in medicine and increasingly so in the behavioural sciences and social programme evaluation fields. However, RCTs produce equivocal results due to lack of statistical power, sampling error, measurement error, different statistical techniques, heterogeneity of interventions and confounding variables (Cook & Campbell, 1979; Rosenthal, 1984; Hedges & Olkin, 1985; Cohen, 1988; Cook et al, 1992). In order to overcome the limitations of individual studies and the difficulties in qualitatively combining the results from many studies, the use of systematic reviews that include the statistical technique of ‘meta-analysis’ has become widespread. Meta-analytical techniques were developed during the 1960s and 1970s but became well known with the publication of the systematic review of the effectiveness of psychotherapy by Glass, McGaw & Smith (1981).