Yale School of Medicine researchers are closer to figuring out the mechanisms working behind bipolar disorder, a condition that affects more than 2 million Americans, according to figures from the National Institute of Mental Health.

Preliminary findings will be published in the next issue of Biological Psychiatry by the team led by Yale’s Dr. Hilary Blumberg, indicating that people with bipolar disorder undergo an accelerated decrease in brain volume from early adolescence to young adulthood in the area of the brain associated with controlling impulses and moods. The team of scientists also observed that medication seemed to reverse some of the abnormalities.

The study contributes to brain development research, especially during the teenage years, Blumberg, a professor of psychiatry and director of the Mood Disorders Research Program, said.

Bipolar disorder, also known as manic depression, is one of the most common mental illnesses and a chronic medical disorder. Patients with Bipolar disorder are marked by having emotional ups, downs or both. These emotional variations manifest themselves in depression, elevated emotions, and impulsiveness.

“It affects between one and two people in 100,” said Dr. Leon Rosenberg, a former dean of the Yale School of Medicine who lives with bipolar disorder. “It’s most usual age of onset is late teenage years, so it is a very significant issue for university-age students.”

Rosenberg added that bipolar disorder is a serious issue because about one in five people who do not seek treatment end up committing suicide.

Many who have bipolar disorder can control the symptoms with medication, but for some the disorder is disabling, said Dr. John Krystal, a professor of psychiatry and co-author in the study.

Blumberg and her team set out to grasp how the disease progresses and when in a person’s life it presents itself.

To better understand the development, the researchers used magnetic resonance imaging to analyze the brains of 37 individuals of varied ages with bipolar disorder and 56 healthy individuals.

The study showed decreased brain volumes in the ventral prefrontal cortex, an area in the lower part of the brain behind the eyes. This abnormality was observed in young adults with bipolar disorder, especially those who suffered from rapid changes in their moods and those who were not being treated with medicine, Krystal said.

“Some of the classic teaching was that bipolar disorder had its onset in late teenage years, or early adult years,” Blumberg said. “That’s when a patient might have presented for their first treatment or first hospitalization. It seems to be more accepted now that you can have the disorder in the earlier teenage years.”

Blumberg said this study suggests that if bipolar disorder is detected early on in its development, some of its symptoms may be controlled before they ever reveal themselves. But further research is necessary to verify the results, since this is only a preliminary study, mostly due to the selection of the subjects, she said.

“You always want to have a bigger sample,” Blumberg said. “It is a cross-sectional study — different patients were scanned at different ages — so you have to be careful about drawing conclusions about age-associations.”

Blumberg said it is possible that differences attributed to age may have influenced the results, since the individual patients’ brain volume was not monitored over a span of time.