"Traditionally, there has been this distinction between neurological and psychiatric disorders, but it is an artificial distinction," said lead author Russell L. Margolis, M.D. "Indeed, the high rate of psychiatric disorders in these patients suggests that many, if not most, can benefit from treatment, even if the course of the brain disease itself cannot be reversed. Many symptoms can be eased, and the quality of life for these patients and their families can be greatly enhanced."

"Our findings of high rates of psychiatric disorders in Huntington's disease confirm the results of previous studies, and we believe we've found the first well-established link between serious psychiatric disorders and the cerebellum," notes Margolis.

In the study, Margolis and his American colleagues conducted detailed interviews and analyzed brain images of three groups: 31 patients with degenerative cerebellar disease, 21 patients with Huntington's disease, and 29 people without any signs of brain disease.

The researchers found that 77 percent of patients with cerebellar disease had psychiatric disorders, as did 81 percent of Huntington's disease patients, rates nearly double those seen in control subjects (41 percent). Of the patients with cerebellar disease, 68 percent had a mood disorder such as depression compared with 43 percent of Huntington's disease patients and 31 percent of healthy subjects. Personality change was present in 26 percent of cerebellar disease patients, 48 percent of Huntington's disease patients, and none of the healthy patients. Either cognitive disorder or dementia was seen in 19 percent of cerebellar disease patients and 71 percent of Huntington's disease patients.

According to Margolis, Huntington's disease primarily affects the striatum, which helps to regulate movement, emotion, and cognition. The role of the cerebellum has traditionally been thought to be limited to regulation of movement. However, connections between the cerebellum and the cerebral cortex suggest that the cerebellum, like the striatum, might also regulate cognition and emotion.

Comparing these two patient groups allowed the researchers to demonstrate that the cerebellum, like the striatum, does indeed influence cognition and emotion, and that this influence is of potential clinical significance. Individuals within the groups were matched for duration of their disease and level of impairment so that minimally affected individuals were not compared with those with severe disease.

For the control group of people with no signs of neurological disease, the researchers chose people who lived with the patients, usually the spouses, because they are likely to share some of the same psychological and social stresses as the neurology patients. Margolis says spouses were chosen because one of the problems with studying psychiatric problems in patients with brain disease is determining whether a psychiatric problem is from the brain disease itself or is a psychological reaction to having a chronic, debilitating disease.

"We're really excited about what our findings mean for patients with cerebellar disease, since many of their psychiatric problems can be managed with a combination of education, medication and psychotherapy," Margolis added.