- Serotonin hypothesis of winter depression: behavioral and neuroendocrine effects of the 5-HT(1A) receptor partial agonist ipsapirone in patients with seasonal affective disorder and healthy control subjects. Schwartz, P.J., Turner, E.H., Garcia-Borreguero, D., Sedway, J., Vetticad, R.G., Wehr, T.A., Murphy, D.L., Rosenthal, N.E. Psychiatry research. (1999)