Alterations in serotonin functioning are related to which of the following?

• A. Serotonin affects only mood.
• B. Serotonin is not involved in mental illness.
• C. Alterations in serotonin functioning are related to mental illness and drug-induced hallucinations.
• D. Serotonin is primarily a digestive hormone.

Answer: (C)

Serotonin works throughout the brain to influence mood, sleep, appetite, perception, and cognition, so changes in how it functions can contribute to mental illness as well as to how some drugs alter perception. Many hallucinogenic drugs act by stimulating serotonin receptors, particularly 5-HT2A, which can produce drug-induced perceptual changes and hallucinations. While most serotonin is in the gut, its crucial role in CNS signaling makes alterations in its functioning relevant to mental illness and drug effects, not to be read as primarily a digestive hormone.