[Nonspecific factors and variations in biological parameters studied in biological psychiatry]

Some studies found no connection at all between biological parameters and mental illness. There are many reasons for the discrepancies: populations and parameters investigated as well as the method used, widely differed. The discrepancies observed, could also be partly due to several non-specific factors such as age, sex, hormonal status, circadian or circannual variations, and washout period. The authors report here some data gathered in the course of a psychobiological research program on healthy volunteers. Their results indicate that human plateler MAO activity shows an apparent menstrual cycle related variation [3H] IMI binding in human platelets shows circadian variations in summer and some antidepressant drugs have a residual effect on serotoninergic parameters during one month. These studies oblige investigators to be cautious when interpreting biological data in psychiatry. Ideally longitudinal studies should be implemented at the various stages of mental illness.