SEASONAL-VARIATION IN BEHAVIORAL-RESPONSES TO M-CPP IN PATIENTS WITH SEASONAL AFFECTIVE-DISORDER AND CONTROLS

This paper reports the behavioral responses to m-chlorophenylpiperazin e (m-CPP), a serotonin agonist, in patients with seasonal affective di sorder (SAD) and controls during the summer. Results are compared with the responses of SAD patients and controls given m-CPP in the winter. Results of the winter study were reported earlier by our group. Basel ine Hamilton depression ratings in SAD patients were significantly low er in the summer than in winter (p < 0.05). Additionally, in both SAD patients and controls, there were seasonal differences on the National Institute of Mental Health (NIMH) self-rating scale items: ''depresse d affect,'' ''dysphoria,'' and ''functional deficit'' at baseline. The behavioral responses to m-CPP across seasons differentiated patients from normals only in the ''activation/euphoria'' item, on which afar g reater response was seen in patients than in controls during the winte r. This behavioral response may be a state marker for winter depressio n, as it was significantly reduced after light treatment of these pati ents in the winter, and in the summer. SAD patients responded differen tly from controls on ''altered self-awareness'' and ''dysphoria'' inde pendently of seasons, and these responses may be considered as possibl e trait markers for this condition. These results provide further evid ence of a possible deficiency in serotonergic transmission in seasonal affective disorder.