How Psychotherapy Changes the Brain

Abstract

Psychotherapy outcomes and the mechanisms of change that are related to its effects have traditionally been investigated on the psychological and social levels, by measuring changes in symptoms, psychological abilities, personality, or social functioning. Many psychiatrists have also held the unfortunate dichotomized position that psychotherapy is a treatment for “psychologically based” disorders, while medication is for “biologically based” disorders. During1 the past several decades, it has become clear that all mental processes derive from mechanisms of the brain. This means that any change in our psychological2 processes is reflected by changes in the functions or structures of the brain. Straightforward reductionistic stances, however, are unfounded because there is clear evidence that our subjective experiences affect the brain.1 Plastic changes in the brain have been difficult to study in humans, but there has been more success in animal studies. Changes in the brain in relation to experience have been detected at the cellular and molecular levels in animals using different experimental approaches. The advent of functional neuroimaging, including single photon emission CT (SPECT), positron emission tomography (PET), and functional MRI, has made it possible to study changes at the brain systems level (by measuring changes in brain blood flow or metabolisms) and, increasingly, also on the molecular level using SPECT and PET in the living human brain. Brain