Life events and biological vulnerability: a study of life events and platelet MAO activity in depressed patients.

The present study investigated the possible relationship between platelet monoamine oxidase (MAO) activity and life events. From the general hypothesis that the impact of life events should be seen against the background of an individual's vulnerability, it was assumed that low platelet MAO patients would need fewer life events to develop a psychopathological condition and that they would experience more negatively those events that occurred. Patients (n = 127) of both sexes suffering from various kinds of depressive disorders participated in the study. There were 39 unipolar patients, 11 bipolar patients, 43 patients suffering from neurotic-reactive disorder, and 34 patients suffering from an unspecified depressive disorder. No statistically significant differences in MAO activity were found in this series among the diagnostic subgroups. Younger patients predominated among those with the lowest MAO values. As expected, low MAO patients reported a lower number of life events than patients in the highest MAO quartile, and had experienced those events more negatively.