Monoamine hypothesis of depression

Monoamine Hypothesis is a biological theory stating that depression is caused by the underactivity in the brain of monoamines, such as dopamaine, serotonin, and norepinephrine.

In the 1950's the monoamine oxidase inhibitors (MAOIs) and and tricyclic antidepressants were accidentally discovered to be effective in the treatment of depression. These findings and other supporting evidence led Joseph Schildkraut 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 impairments such as schizophrenia also found that too little activity of certain neurotransmitters were connected to these disorders.

The 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 tool in the aiding of our understanding of brain chemistry and explaining pharmacotherapy.