Functional brain asymmetry as a determinative factor in the treatment of depression: theoretical implications.

Depression is characterized by the functional insufficiency of both left and right hemispheres. Patients who respond to antidepressants are characterized by a relatively higher left hemisphere activity in comparison to non-responders, and successful treatment with antidepressants increases left hemisphere activity. Left hemisphere is responsible for the goal-oriented behavior that includes search activity as a state opposite to depression, which accounts for the positive outcome in depression following activation of the left hemisphere. However, it is not a pathogenetic but a palliative treatment, because the core reason for depression is the inability of the right hemisphere to correspond to the demands of the polydimensional environment. The article suggests that in order to achieve stability, treatment has to combine methods that restore left hemisphere activity with methods that restore right hemisphere efficiency.