Andy Thompson, a University of Virginia psychiatrist, and Paul Andrews of Virginia Commonwealth University believe that it does. They wrote that depression is a mechanism for solving social problems through “rumination,” which they call the prioritizing of problem solving and the de-emphasis of distractions.
“The hypothesis is supported by evidence from many levels—genes, neurotransmitters and their receptors, neurophysiology, neuroanatomy, neuroenergetics, pharmacology, cognition, behavior, and efficacy of treatments.”
People who ruminate become depressed more easily. Depression may be a plea for help, or a symbol of defeat. It sharpens the focus on reality.
I believe depression is a mental state that might be advantageous in decision making if it is not severe. It is a recursive condition causing sufferers to loop back to painful ideas or memories, to the exclusion of other thoughts and activities. (Humans experience a number of cyclical patterns, ranging from the metabolic energy cycle to spousal abuse. Depression is just one more of these phenomena.)
Depression causes pain from a triggering thought that is re-visited over and over. In contrast, dopamine is a chemical in the brain that triggers pleasure from something (like chocolate) that is experienced repeatedly; it defines our motivations when it exists in its moderate state, and addiction when it exists in the extreme. Depression and dopamine have similar loop-back mechanisms — beneficial when mild, but damaging when they become overpowering.
Depression affects brain activity in the left ventrolateral prefrontal cortex (whereas dopamine receptors are in the midbrain and the hypothalamus). Three neurochemical pathways influence depression: the hypothalamic-pituitary-adrenal (HPA) axis; the seratonin pathway, and the noradrenaline pathway. Some depressions are triggered by chemical imbalances, while others are caused by stressful or traumatic events.
Resolving depression is to some extent a matter of brain chemistry. But studies tell us that the most significant improvement results from conscious thought. Patients receiving antidepressants were more than twice as likely to relapse as those receiving cognitive behavioral therapy alone or in combination with drugs. This positive effect from self-awareness and reflection involves deconstructing the vicious cycle between the thoughts and the pain. It is a therapeutic exploration of causes, context and solutions surrounding the triggering event; and a reintroduction of other life activities or distractions.The lower recidivism after therapy means to me that drugs may reduce the pain and address the symptoms of depression; but working alone they fail to adequately attack the cause.
Depression is positively associated with alertness and productivity. One survey of writers found that 80% met the diagnostic criteria. Another found that an induced sense of melancholy resulted in a more accurate assessment of rumors and strangers. A negative mood (for example, “self-handicapping”) promotes complex decision-making. I believe people who are sad or depressed are generally dealing with a larger set of sensory data and engaging in more introspective feedback. This often makes them more focused and creative.
Wisdom Isn’t Cheap, and We Pay for It with Pain, by Jonah Lehrer, The New York Times Magazine, February 28, 2010, p. 40.
The bright side of being blue: Depression as an adaptation for analyzing complex problems. By Andrews, Paul W.; Thomson Jr., J. Anderson. Psychological Review. Vol 116(3), Jul 2009, 620-654.
 This theory directly correlating the amount of introspection with the susceptability to depression is espoused by Yale University psychology professor Susan Nolen-Hoeksema.