What biological theory is involved in the etiology of Major Depressive Disorder related to neurotransmitter functioning?

The Catecholamine hypothesis is considered a significant biological theory in understanding the etiology of Major Depressive Disorder, particularly in relation to neurotransmitter functioning. This hypothesis suggests that mood disorders, including depression, may be linked to deficiencies in certain neurotransmitters, particularly catecholamines such as norepinephrine.

Research indicates that low levels of norepinephrine can contribute to symptoms commonly associated with depression, such as lack of motivation, fatigue, and diminished interest in activities. This understanding has led to the development of antidepressant medications, such as tricyclics and monoamine oxidase inhibitors, which aim to increase the availability of norepinephrine and other neurotransmitters, thereby alleviating depressive symptoms.

This framework contrasts with other theories, such as the Learned Helplessness Model, which focuses on behavioral aspects and the individual's perception of control; Beck's Cognitive Triad, which emphasizes cognitive factors and negative thinking patterns; and the Behavior Therapy Model, which is centered on changing maladaptive behaviors. Each of these contributes to our understanding of depression but does not specifically address the biological underpinnings involving neurotransmitter dysfunction in the same way the Catecholamine hypothesis does.