One hundred and fifty-four reports were identified, of which 76 met the criteria for inclusion; 54 were case series and 22 were case–control studies. The median proportion of cases with mental disorder was 91% (95% CI 81–98%) in the case series. In the case–control studies the figure was 90% (88–95%) in the cases and 27% (14–48%) in the controls. Co-morbid mental disorder and substance abuse also preceded suicide in more cases (38%, 19–57%) than controls (6%, 0–13%). The population attributable fraction for mental disorder ranged from 47–74% in the seven studies in which it could be calculated. The effects of particular disorders and sociological variables have been insufficiently studied to draw clear conclusions.