A 30-year-old young man talks a lot about his general appearance. He claims that his general appearance and the muscles in his hands specifically appear small, and although others tell him that he is in very good health, he firmly believes that others compliment him about that, and in fact they make fun of him. His body has become thinner and his muscles have atrophied, and in the past he has tried many things, including exercise and some medications to increase the size of his muscles, but he still has the same feeling about his general appearance.
Explain how psychotherapeutic theories (behavioral, cognitive behavioral, psychoanalytic) explain the cause of the disorder experienced by the reported case?