Despite continuing progress in the treatment and prophylaxis of affective disorders, mental depression remains a major world health problem. Statistics on mental depression vary to some extent; however, they all attest to the high frequency of this disorder in the population. The lifetime risk of any one of us suffering from a depression of clinical severity has been estimated at between 10 and 15% (Weissman and Klerman, 1978). According to recent WHO reports, at least one hundred million people are suffering from mental depression of clinical intensity at any time (Sartorius, 1979).