This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mood Disorders, Subject name: Psychiatry
The clinical effects of the antidepressant drugs is mainly based on: 
Select and explain. 
A. Change in neurotransmitter receptor sensitivity, B. Decreased levels of neurotransmitters, C. Change in efficacy of neurotransmitters, D. None of the above
A: Change in neurotransmitter receptor sensitivity
Answer: A: Change in neurotransmitter receptor sensitivity 
Explanation: Secondary to increased neurotransmitter levels by anti depressants, the receptor sensitivity changes over a course of time and that is responsible for antidepressant effect.