In 87 patients with affective spectrum disorders (58% suffering from a major depressive episode - MDE) the potential association between platelet MAO-B activity and suicidality was examined. Fifty-nine of the patients had committed suicide attempt recently (SA -'suicide attempters'), 28 patients were acutely depressed without having shown suicidal thoughts or suicidal behaviour in the past (NA -'non-suicide attempters').