Hugh Pickens writes "Paul W. Andrews and J. Anderson Thomson, Jr. argue in Scientific American that although depression is considered a mental disorder, depression may in fact be a mental adaptation which provides real benefits. This is not to say that depression is not a problem. Depressed people often have trouble performing everyday activities, they can't concentrate on their work, they tend to socially isolate themselves, they are lethargic, and they often lose the ability to take pleasure from such activities such as eating and sex. So what could be so useful about depression? 'Depressed people often think intensely about their problems,' write the authors. 'These thoughts are called ruminations; they are persistent and depressed people have difficulty thinking about anything else. Numerous studies have also shown that this thinking style is often highly analytical. They dwell on a complex problem, breaking it down into smaller components, which are considered one at a time.' Various studies have found that people in depressed mood states are better at solving social dilemmas and there is evidence that people who get more depressed while they are working on complex problems in an intelligence test tend to score higher on the test (PDF). 'When one considers all the evidence, depression seems less like a disorder where the brain is operating in a haphazard way, or malfunctioning. Instead, depression seems more like the vertebrate eye — an intricate, highly organized piece of machinery that performs a specific function.'"