Seasonal variations of the dexamethasone suppression test in depression compared with schizophrenia: a gender effect

The circannual results of the dexamethasone suppression test (DST) were compared in depressed and schizophrenic patients for the periods November-February and March-October. During the winter months, female depressive and schizophrenic patients had lower rates of DST nonsuppression as well as lower concentrations of post-dexamethasone plasma cortisol, compared to the March-October period, despite similar pre-dexamethasone cortisol levels. Male depressed patients had lower pre-dexamethasone cortisol levels during the winter months while male schizophrenics had higher pre- and post-dexamethasone cortisol levels and higher rates of DST nonsuppression. This may suggest less disturbance of HPA axis function in winter months in depressed patients, mostly females, and confirms findings from some previous studies. A gender effect of DST seasonality was also demonstrated, with male schizophrenic patients presenting a reverse DST nonsuppression pattern compared with female depressive and female schizophrenic patients.