Authors studied 109 patients with eating disorders, including 49 with anorexia nervosa (AN) and 60 with bulimia nervosa (BN), using psychopathological and experimental/psychological methods, psychometric scales and follow-up. Four variants (2 AN and 2 BN) of clinical presentations and dynamics of affective disorders were singled out. It has been shown that many features of their symptoms and responses of patients to the complex therapy (diet-, psycho- and pharmacotherapy) depend on the belonging of AN or BN to a group of borderline mental disorders or to endogenous diseases. Taking into account the revealed features of affective disorders, the authors have formulated recommendations for treatment tactics and prevention measures for these groups of patients.