The chief problem with the view of depression as a consequence of a "chemical imbalance in the brain" is the fact that depression can be both triggered by and resolved by life events. The misconception the commercials foster is that the brain somehow develops a chemical imbalance and the result is depression, occurring in a single directional process. In fact, the relationship between brain chemistry and experience is a two-directional phenomenon: Life experience affects brain chemistry at least as much as brain chemistry affects life experience. (http://www.helpguide.org/mental/medications_depression.htm)
The majority of recent functional imaging studies have demonstrated a reduction in activity most pronounced in the left prefrontal cortical and limbic areas in individuals with recurrent or chronic depressive disorders. The reduction in activity level is evidenced by decreased blood flow with decreased oxygen or glucose utilization in those neuroanatomical areas. (Patten, S. B. and L. M. Metz, 1997).
Some researchers reported that, recently depressed patients lose substantial brain tissue. Using PET, researchers found that the activity in the prefrontal cortex is decreased in individuals with depression. They have also demonstrated a reduction in frontal lobe gray matter, an average of 39 percent reduction in people with bipolar and 48 percent in people with unipolar depression.
What is not yet clear is whether the reduction in gray matter volume in the prefrontal areas is a developmental problem or the result of recurrent illness. Also unknown is whether successful treatment of depression with antidepressants reverses the brain tissue loss.
The first modern biological models for chemical abnormalities in depression gained prominence in the middle of the twentieth century. They proposed that low brain levels of a specific chemical or neurotransmitter cause depression. Research focused on determining which of the commonly recognized neurotransmitters--norepinephrine (NE), dopamine (DA), and serotonin (5 -hydroxytryptamine, or 5 -HT)--was important in the genesis of depression......
