This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
Drug of choice in MDP is: 
Select and explain. 
A. Lithium, B. Amphetamine, C. Diazepam, D. Alprazolam
A: Lithium
Answer: A: Lithium 
Explanation: Lithium