In major depressive disorder, a commonly taught neurochemical finding is a relative deficiency of which neurotransmitter?

• A. Dopamine
• B. Serotonin (5-HT)
• C. Gamma-aminobutyric acid (GABA)
• D. Acetylcholine

Answer: (B)

Verified step by step guidance

1. Understand that major depressive disorder (MDD) is often linked to imbalances in brain chemistry, particularly involving neurotransmitters that regulate mood and emotion.
2. Recall that neurotransmitters are chemical messengers in the brain, and certain ones are commonly associated with depression, such as serotonin, dopamine, and norepinephrine.
3. Identify that serotonin (5-HT) is widely studied and implicated in MDD due to its role in mood regulation, sleep, and appetite, and that a relative deficiency of serotonin is a key neurochemical finding in depression.
4. Recognize that while dopamine and other neurotransmitters like GABA and acetylcholine have roles in brain function, the classic and most commonly taught deficiency in MDD is serotonin.
5. Conclude that the correct answer is serotonin (5-HT) because it is the neurotransmitter most consistently linked to the neurochemical basis of major depressive disorder.