Chemical Imbalance

Chemical imbalance is one hypothesis about the cause of mental illness. Other causes that are debated include psychological and social causes.

The basic concept is that neurotransmitter imbalances within the brain are the main causes of psychiatric conditions and that these conditions can be improved with medication which corrects these imbalances. The phrase originated from the scientific study of brain chemistry. In the 1950s the monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants were accidentally discovered to be effective in the treatment of depression.

These findings and other supporting evidence led scientist Joseph J. Schildkraut (1934–2006) to publish his paper called "The Catecholamine Hypothesis of Affective Disorders" in 1965. Schildkraut associated low levels of neurotransmitters with depression.

Research into other mental illnesses such as schizophrenia also found that too much activity of certain neurotransmitters such as dopamine was correlated to these disorders. In the scientific community this hypothesis has been referred to as the "Monoamine hypothesis". This hypothesis has been a major focus of research in the fields pathophysiology and pharmacotherapy for over 25 years and led to the development of new classes of drugs such as SSRIs (selective-serotonin reuptake inhibitors).

This conceptual framework has been challenged within the scientific community, though no other demonstrably superior hypothesis has emerged. While the hypothesis has been shown to be simplistic and lacking, there is sufficient evidence to consider it as a useful heuristic in the aiding of our understanding of brain chemistry and explaining pharmacotherapy.

Wayne Goodman, Chair of the US Food and Drug Administration Psychopharmacological Advisory Committee, has described the serotonergic theory of depression as a "useful metaphor" for understanding depression, though not one that he uses with his own psychiatric patients. Recently, psychiatrist Peter Kramer stated that the serotonin theory of depression had been declared dead prematurely. Kramer argues that recent scientific research actually shows a definitive role for serotonin deficiency in depression. An analysis of the studies Kramer cites argues that such statements are premature.