The Nurse Finds That the Client with a Somatoform Disorder

The nurse finds that the client with a somatoform disorder has physical symptoms present, but there is no evidence of physiologic disease. The client may have decreased amounts of serotonin and endorphins, causing the client to experience an increased sensitivity to pain. This explanation of the client's symptoms is based in:

A) Biologic theory.
B) Genetic theory.
C) Humanistic theory.
D) Communication theory.