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Serotonin Theory of Depression


For decades, a “chemical imbalance” in the brain, especially that of a chemical called serotonin, has been widely seen to be responsible for depression — a view that has promoted the use of antidepressants as part of the treatment for the condition.

  • Researchers from University College London who carried out a “comprehensive review of the major strands of research on serotonin” have now reported that “there is no convincing evidence that depression is associated with, or caused by, lower serotonin concentrations or activity”.


GS III- Science and Technology

Dimensions of the Article:

  1. What is the serotonin theory of depression?
  2. What exactly is serotonin?
  3. What is the conclusion of the new research?

What is the serotonin theory of depression?

  • “The idea that depression is the result of abnormalities in brain chemicals, particularly serotonin (5-hydroxytryptamine or 5-HT), has been influential for decades, and provides an important justification for the use of antidepressants,”
  • Depression was first linked to lowered serotonin levels in the 1960s, and the theory gained wide acceptance in the 1990s with the advent of Selective Serotonin Reuptake Inhibitor (SSRI) antidepressants, which temporarily increase the availability of serotonin in the brain.
  • The idea is endorsed by official institutions like the American Psychiatric Association, which says “differences in certain chemicals in the brain may contribute to symptoms of depression”.

What exactly is serotonin?

  • It is a kind of neurotransmitter, a chemical that helps transmit messages or signals from one nerve cell to another for communicating.
  • Serotonin helps regulate mood, sleep, appetite, and other major aspects of daily functioning.

What is the conclusion of the new research?

  • Over the years, several studies have questioned the serotonin theory.
  • The new study conducted an “umbrella review”, collating existing overviews of the principal areas of relevant research on serotonin and depression.
  • The intention was to establish “whether the current evidence supports a role for serotonin in the aetiology of depression, and specifically whether depression is associated with indications of lowered serotonin concentrations or activity”.
  • The conclusion of the study: “The serotonin theory of depression has been one of the most influential and extensively researched biological theories of the origins of depression. Our study shows that this view is not supported by scientific evidence. It also calls into question the basis for the use of antidepressants.”
  • People who were taking or had previously taken antidepressants showed evidence that these drugs may actually lower the concentration or activity of serotonin, the study showed.
  • “Although viewing depression as a biological disorder may seem like it would reduce stigma, in fact, research has shown the opposite, and also that people who believe their own depression is due to a chemical imbalance are more pessimistic about their chances of recovery,”
  • According to the researchers, there are other explanations for the effect that antidepressants have on a person.
  • Drug trials show they are “barely distinguishable from a placebo (dummy pill) when it comes to treating depression,” and antidepressants appear to have more of a generalised emotion-numbing effect on people’s moods.

-Source: Indian Express

December 2023