Biologic Theories of Causation

Genetic Theories. Scrutiny of major depression in family, twin and adoption studies demonstrates that genetic influences undoubtedly play a substantial role in the etiology of mood disorder. Major depressive disorder is 1,5 to 3 times more common among first-degree biologics relatives of persons with this disorder than among the general population. Alcoholism in a biologic parent has been implicated as a probable marker for genetic vulnerability to depression. Currently, a major research focus developing a more accurate paradigm regarding the contribution of genetic factors to the development of mood disorder.

Biochemical Theories. Neurotransmitters and receptors hypotbesis considerable evidence now indicates that the secretion of the hypothalamic hypophysiotropic hormones is controlled by many of the classical neurotransmitters such as serotonin, acetylchloline, norepinephrine, dopamine, and ץ-aminobutyric acid (GABA) – all previously posited to be involved in the pathophysiology of mood as well as anxiety disorder. Other significant neurotransmitter research is focused on the receptors and transporters of these molecules, as well as the enzymes that control their production and catabolism.

Neuroendocrine and neuropeptide hypotbesis. Unipolar depression is associated with multiple alterations, specifically of the hypothalamic – pituitary – adrenal axis, the hypothalamic growth ‘iormone’ axis, and the hypothalamic-pituitary-gonadal axis. In addition, there is mounting evidence that components of neuroendocrine axes (eg. Neuromodulatory peptides like corticotrophin-releasing factor) may themselves contribute to depressive symptomatology.

Psychoneuroimmunology. This recently emerged major area of psychiatric research involves the study of interactions among behavioral, neutral, endocrine, and immune processes of adaptation. Each serving homeostatic and regulatory functions. The sequela of altered immune functioning, in terms old specific psychiatric disease pathogenesis, hs yet to be elucidated.