Difficulties Experiencing Simple Pleasures May Be Caused By Smaller Brains

Yet another biological link between mental illnesses like depression and schizophrenia and brain physiology has been discovered by scientists at the Douglas Mental Health University Institute in Montreal.

Anhedonia, or the inability to experience simple pleasures as strongly as the average person, is a symptom of illnesses such as depression. It also may be because of a smaller area of the brain in which pleasures are processed. Douglas researchers have discovered that patients who suffer from anhedonia also have smaller area of the brain called the anterior caudate. This area of the brain, located in the center regions, is responsible for pleasure and reward.

According to MRI scans of patients with varying degrees of anhedonia, those who suffered the most from this ailment processed pleasurable images, such as a beautiful waterfall, in the part of the brain responsible for cognition rather than in the anterior caudate. The twenty-nine patients chosen for the study had no previously diagnosed mental illness. Their degrees of anhedonia were measured by a questionnaire that contained questions such as "I generally agree that making love is an intense pleasure" that were rated on a scale from "strongly disagree" to "strongly agree", with those choosing "strongly disagree" on such questions to be considered highly anhedonic.

"The hypothesis is that because they don't feel pleasure as high as other people, when they analyze positive information, they have to process it at a more cognitive level," explained lead author Philippe-Olivier Harvey to the Montreal Gazette. "So there is a genuine lack of pleasure and they have to compensate for this by an overactivation of this (cognitive) region of the brain."

In those who enjoyed pleasure normally, this cognitive area of the brain, located just behind the forehead, was not active.

These findings are significant for advocates of the biological connections of various mental illnesses. It also will make treatment of some forms of depression and schizophrenia easier as a simple MRI scan can tell physicians why the patient is having a difficult time feeling pleasure and adjust treatment accordingly.

"It has been well established that anhedonia is a key symptom of major depression and schizophrenia," said Douglas researcher Martin Lepage. "We chose to study this core symptom in hopes of finding a vulnerability marker to better diagnose these mental illnesses."