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Causes of Depression

Substantial evidence from neuroscience, genetics, and clinical investigation shows that depressive illnesses are disorders of the brain. More specifically, research has shown that when a person is depressed, that person's brain is functioning differently from the brain of a non-depressed person. This means that there is a correlation between the person's mood state (depression) and what is happening in that person's brain. However, the precise cause of these changes in brain chemistry continue to be a matter of intense research. That means that we still do not know which comes first, the depressed mood or the change in brain chemistry.

Modern brain imaging technologies reveal that, in depression, neural circuits responsible for the regulation of moods, thinking, sleep, appetite, and behavior fail to function properly, and critical neurotransmitters are out of balance. Neurotransmitters are chemicals in the brain cells that send messages from one part of the brain to another part of the brain. Studies of brain chemistry, including the effects of antidepressant medications, continue to inform our understanding of the biochemical processes involved in depression. In fact, effective treatment of depression, either with therapy or medication, results in changes in the brain chemistry back to a more normal state. Science can provide a fairly good explanation regarding why the antidepressant medication causes a change in brain chemistry, but not why psychotherapy, especially cognitive and interpersonal therapy, causes a change in brain chemistry.

In some families, depressive disorders seem to occur generation after generation. However, depression can also occur in people with no family history of depression. Genetics research indicates that risk for depression results from the influence of multiple genes acting together with environmental or other nongenetic factors. In plain English, this means that depression seems to result from a combination of genetic, environmental and cognitive factors. The environmental factors include life problems, both minor and major, such as job loss, divorce, loss, and interpersonal conflict. Cognitive factors include how we think about the world, how we evaluate problems, and whether we believe we can handle the problems we are facing. (More Information on Cognitive Factors Affecting Depression) Depression seems to result from some combination of these factors.

If a combination of genetic, cognitive, and environmental factors is involved in the onset of a depressive disorder, then anyone can become depressed. Trauma, loss of a loved one, a difficult relationship, a financial problem, or any stressful change in life patterns, whether the change is unwelcome or desired, can trigger a depressive episode in vulnerable individuals. If a person has strong genetic factors influencing depression, then that person might become depressed with less severe life problems. But, we are all vulnerable to depression if our life problems are overwhelming. After the first episode of depression, later episodes may occur without an obvious environmental cause.


Men: Depression and Bipolar Disorder: