Based on a systematic review of 17 medical studies, a recently published paper has raised questions and sparked debate about the chemical imbalance theory of depression. Although the study did not perform additional research, after synthesizing and evaluating evidence in the principal relevant areas, the authors conclude the longstanding theory is unproven.
Serotonin is a monoamine neurotransmitter, a chemical that regulates mood, sleep, appetite, and sexual desire. The chemical imbalance theory suggests that depression is caused by lowered serotonin levels in the brain.
The paper, published July 20 in the journal Molecular Psychiatry by a multi-national team of researchers, is entitled “The serotonin theory of depression: a systematic umbrella review of the evidence.” The paper questions the “chemical imbalance” theory that began in the 1960s, based on the premise that reduced serotonin activity causes depression. This hypothesis was derived from the fact that the first two specifically antidepressant drugs, discovered in the 1950s, were both shown to increase brain levels of serotonin. Therefore, early experiments assumed a causal relationship between serotonin and depression….