Modern psychotherapy has its roots in behavioral therapy, which is also referred to as behaviorism. This school of thought teaches that all human behaviors are conditioned responses to external stimuli — what we'd refer to as our environment.

A pioneer in this field was Ivan Pavlov, a Russian researcher whose name became a household word. He trained dogs to salivate at the sound of a bell, because they had been conditioned to receive food after the bell rang. Another pioneer was B.F. Skinner, an American psychologist who carried this work over into human subjects. His theory of operant conditioning held that living creatures operate on their environment.

If the results of their operating produce a desirable result, they'll continue doing whatever caused the good thing. If the results turn out to be bad, they'll stop whatever caused the bad thing. Behavior modification is a current form of therapy that draws on Skinner's work. Essentially, you change your behavior and you get different results.

If you're suffering from depression, lifestyle changes are an important component of therapy. But perhaps the two biggest names in the field of psychology are Sigmund Freud and Carl Jung, who you'll read about in the following two sections. (You'll also read about two more important figures, Albert Ellis and Aaron Beck.

Sigmund Freud

Sigmund Freud was a medical doctor specializing in neurology. Freud was fascinated with the workings of the unconscious mind — those thoughts that occur when you are sleeping. According to Freud, adult depression and anxiety were related to childhood experiences, and dreams held the answers for treating these disorders.

During REM sleep, the rational and reasoning portion of the brain is not at the helm, so all inhibitions can break loose. That means that you can think about very painful experiences that your awake mind keeps repressed. Analyze your dreams, and you can relieve the symptoms of depression. This was the theory Freud discussed in his Interpretation of Dreams. Freud also found that when his patients discussed their symptoms, problems, and concerns with him, their depression symptoms decreased.

Freud also studied the sexual causes of psychological disorders; but, in this regard, his work has largely been bypassed, as medical breakthroughs have begun to unravel the neurochemical aspects of depression.

Carl Jung

Carl Jung is considered the father of analytical psychology. With a more spiritual bent than Freud, Jung believed that there was a “collective unconscious” shared by all humanity. Where Freud focused on sexuality and aggression, Jung focused on the spirit. Jungian psychoanalysis, therefore, takes a holistic approach to therapy and is used widely today. Jungian therapy is not open-ended; the goal is to be able to function without long-term therapy.

Jung's philosophy had much in common with yoga's meditative aspects, which also seek collective consciousness. Jung also developed the concepts of the extroverted and the introverted personality styles.