This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neurotic, Stress Related and Somatoform Disorders, Subject name: Psychiatry
Which of the following is LEAST useful in treatment of OCD? 
Select and explain. 
A. Clomipramine, B. SSRIs, C. Cognitive behavioral therapy, D. Systematic desensitization
D: Systematic desensitization
Answer: D: Systematic desensitization 
Explanation: SSRIs, Clomipramine and CBT are all first line treatment. Systematic desensitization is least effective of all.