Which biochemical factor is described as playing a role in depression in the material?

• A. Serotonin excess
• B. Dopamine excess
• C. GABA excess
• D. Acetylcholine excess

Answer: (A)

Mood regulation hinges on a balance of neurotransmitters, and this item focuses on how that balance, specifically involving serotonin, relates to depression. In the material, an excess of serotonin activity is described as playing a role in depressive symptoms. This means that when serotonin signaling is higher than normal, it can disrupt mood regulation in a way that contributes to depression, possibly through receptor changes or altered downstream pathways that blunt the normal mood-promoting effects. The other neurotransmitters listed aren’t described in that material as contributing to depression in the same way, so the serotonin excess is the factor the text uses to explain the depressive state.