Psychotherapy:

Treatment designed to relieve specific emotional or behavioral symptoms and enhance personal growth.

Health Psychology:

The application of psychological knowledge and methods to promote and maintain mental and physical health. The goal is to prevent, assess and treat psychological symptoms contributing to distress.     (from Millon, 1982)

Neuropsychology:

The study of the relation between brain function and behavior.      (Kolb & Wishaw, 1985)