3 and a fraction mayor may not respond to treatment. On the behavioral level, animal research shows that a variety of experimental conditions can induce de pression. The same is true in the field of treatment, where pharmacologically highly different drugs can equally alleviate depression in animals and hu mans. The question as to whether this is due to a heterogeneity of depressive subjects based on different pathogenetic mechanisms is open to discussion. We can look for common features of all possible causal factors in the hope of finding a single basic mechanism. Many divergent findings may also be ex plained as peripheral changes of a highly complicated dynamic system. In the field of psychopharmacology, a circular reasoning has become evident in the sense that originally the clinical antidepressive response was founded on empirical grounds only. In a second step, an attempt was made to characterize some clinically active compounds pharmacologically, and in a third, further compounds were developed based on aspects of the pharmaco logical profiles. Moreover, the post hoc development of a pharmacological screening method has the serious disadvantage of delaying breakthroughs into new fields.

Inhalt
The Scope of Depression.- The Epidemiology of Bipolar and Nonbipolar Depression: Rates and Risks.- Depression and Affective Disorder in Later Life.- Gender and Depression.- Recent Life Events and Depression.- Vulnerability to Depression: The Lack of Social Support Does Not Cause Depression.- Stress, Conflict, and Depression.- Separation Models and Depression.- Learned Helplessness An Animal Model Revisited.- Neurobiologic Dimensions of Depression and Mania.- Current Status of Genetic Research in Affective Disorders.- Neuroendocrine Function in Depression.- Opioid Systems and the Regulation of Mood: Possible Significance in Depression?.- Neurophysiologic Studies of Depression: State of the Art.- Chronobiology of Depression.- New Research Techniques for Studying the Functional Anatomy of Depression.- Depression and Altered Neurotransmission States, Traits, and Interactions.- Pharmacological Models of Depression.- Heuristically Important Mood-altering Drugs.- Mode of Action of Antidepressant Drugs Primary Effects.- Mode of Action of Antidepressant Agents and ECT Adaptive Changes After Subchronic Treatment.- Risk Factors Group Report.- Animal Models Group Report.- Functional Indices of Biological Disturbance Group Report.- Neurotransmission Group Report.- List of Participants.- Author Index.