From advisory systems that understand emotional attitudes toward medical outcomes, to wearable computers that compensate for communication disability, to computer simulations of emotions and their disorders, the research agendas of medical informatics and affective computing-how and why to create computers that detect, convey, and even have emotions increasingly overlap. Some psychiatric and neurological researchers state their theories in terms of actual or hypothetical computer programs. Adaptive intelligent systems will increasingly rely on emotions to compensate for their own conflicting goals and limited resources-emotional reactions about which psychiatrists and neurologists have special insights. DEP2 (Depression Emulation Program 2) is a computer simulation of adaptive depression-learning from explainable patterns of failure in autobiographical memory-that simulates many depressive behaviors. In the terminology of fault-tolerant computing, adaptive depression involves fault detection (triggered by failure), fault location (strategic retreat and failure diagnosis), and fault recovery (return to on-line operation). DEP2 relies on subsystems whose structures and behaviors are based on popular hypotheses about left and right brain hemispheric function during depression and emotion. DEP2 and its predecessors, DEP and DEPlanner, are relevant to psychiatric and neurological informatics, and to the design of adaptive autonomous robots and software agents.