"Using two large nationally representative studies, we found that there was a strikingly high peak prevalence of bipolar disorders in emerging adulthood," said David Cicero, doctoral student in the Department of Psychological Sciences in the College of Arts and Science
and lead author of the paper. "During the third decade of life, the prevalence of the disorder appears to resolve substantially, suggesting patients become less symptomatic and may have a greater chance of recovery."
By examining the results of two large national surveys, MU researchers found an "age gradient" in the prevalence of bipolar disorder, with part of the population appearing to outgrow the disorder. In the survey results, 5.5 to 6.2 percent of people between the ages of 18 and 24 suffer from bipolar disorder, but only about 3 percent of people older than 29 suffer from bipolar disorder.
"Young adults between the ages of 18 and 24 are going through significant life changes and social strain, which could influence both the onset and course of the disorder," said Kenneth J. Sher, Curators' Professor in the Department of Psychological Sciences and co-author of the study. "During this period of life, young adults are exploring new roles and relationships and begin to leave their parents' homes for school or work. By the mid 20s, adults have begun to adjust to these changes and begin to settle down and form committed relationships."
Researchers predict the prevalence of the disorder also could be affected by brain development, particularly the prefrontal cortex. The prefrontal cortex, the very front part of the brain, is thought to control perception, senses, personality and intelligence. In particular, it controls reactions to social situations, which can be a challenge for people with bipolar disorder.
"The maturing of the prefrontal cortex of the brain around 25 years of age could biologically explain the developmentally limited aspect of bipolar disorder," Cicero said. "Other researchers have found a similar pattern in young adults with alcohol or substance abuse disorders."
While some scholars suggest that the difference could be due to discounting factors such as early mortality, the sheer number of those who are recovering rules out this possibility, Sher said.
The study, "Are There Developmentally Limited Forms of Bipolar Disorder?" was published in the Journal of Abnormal Psychology. It was co-authored by Cicero, Sher and Amee Epler, a doctoral student in the Department of Psychological Sciences.