Selected Aspects of Amine and Receptor Hypotheses of Affective Illness

The role of catecholamines and indoleamines in affective illness and research strategies for investigating their mechanisms of action are reviewed. These strategies include studies of drugs which alleviate or exacerbate manic or depressive symptoms, or which affect the availability or activity of neurotransmitters, their precursors, or their degradative enzymes. Other approaches include investigation of endocrine systems and catecholamine metabolites in body fluids. The authors find that the catecholamine hypothesis can be divided into four separate theories: depression is caused by a functional decrease in either norepinephrine or dopamine, and mania is caused by a functional increase in one or the other of these neurotransmitters. Functional decreases in serotonin have also been proposed to cause depression. The authors discuss the evidence for these hypotheses.