The multiple interactional biological processes that might lead to depression and gender differences in its appearance.

Several neurotransmitter systems have been implicated in the pathophysiology of depression. Gender differences have been demonstrated in some functions that involve these systems, mostly norepinephrine, serotonin, dopamine and acetylcholine. Several hormonal systems have been shown to be altered in depression and gender differences were demonstrated in their activity as well, notably in thyroid hormones and the hypothalamic-pituitary-adrenal system. Most gender differences in brain systems and their hormonal modulators might be attributed to developmental and state influences of gonadal hormones. It is suggested that gender differences in mechanisms that might underlie formation of depressive symptoms might be related mostly to interactional processes and destabilization of balance among multiple factors or circuitry in the central nervous system. Indeed, gender differences in specific neurotransmitters and hormonal systems can be demonstrated as well.