Teens Who Get Moving Leave Mental Illness Behind

Regular physical activity is associated with a substantially reduced risk for some, but not all, mental disorders, Andreas Stroehle, M.D., an assistant professor of psychiatry at Charity-University Medicine Berlin, and colleagues reported in the November Psychological Medicine.

Their study appears to be the first large-scale one to explore prospectively the relationship between exercise and a range of mental disorders. The study also focused on the age group most vulnerable to the development of mental illness—youth.

More than 2,500 subjects were randomly selected for the study from the 1994 government registries of all residents aged 14 to 24 in metropolitan Munich and surrounding counties. The subjects were assessed with the DSM-IV Composite International Diagnostic Interview both at the start of the study and in the subsequent four years. This instrument covers anxiety, eating, mood, somatoform, and substance disorders.

Subjects were also evaluated at the start of the study regarding the amount of physical exercise in which they engaged. The researchers rated them as“ regular exercisers” if they engaged in exercise daily or several times a week, as “non-regular exercisers” if they engaged in exercise one to four times a month, or as “non-exercisers” if they engaged in exercise less than once a month or not at all. At the start of the study, half the subjects were found to be regular exercisers, 15 percent non-regular exercisers, and 35 percent non-exercisers.

The researchers then looked for links between the amount of exercise subjects engaged in at the start of the study and the development of various mental disorders over the next four years.

Compared with subjects who did not exercise, subjects who engaged in regular exercise or in non-regular exercise had a significantly lower incidence of any mental disorder, and specifically a significantly lower incidence of agoraphobia with or without panic disorder, any anxiety disorder, any somatoform disorder, a specific phobia, dysthymia, and posttraumatic stress disorder. Moreover, major depressive disorder and substance use disorders were lower in the regular and non-regular exercisers than in the non-exercisers, although the differences were not statistically significant. These findings held even when educational status, body mass index, other mental disorders, and impairment days due to physical problems were taken into account.

However, there was no significant link between physical exercise and eating disorders. And subjects who exercised regularly or non-regularly at the start of the study were actually found to be at a significantly greater risk of being diagnosed with bipolar disorder than were those subjects who did not exercise at the start of the study.

Thus, physical exercise may help safeguard people from some types of mental illnesses, but not others, Stroehle and his team concluded. “Further examination of the evidently complex mechanisms and pathways underlying these associations might reveal promising new research targets and procedures for targeted prevention,” they added.

“This is an interesting study,” Ronald Kamm, M.D., said in an interview. Kamm is a sport psychiatrist based in Oakhurst, N.J., and the immediate past president of the International Society for Sport Psychiatry. One of the findings that surprised him, he said, was that teens who were physically inactive were no more prone to major depression than were teens who were physically active. “Maybe teenagers are more immune than older people to the effect of inactivity in bringing on depression,” he said.

Another finding that surprised him, he said, was that teens who engaged in physical activity were at significantly greater risk of being diagnosed with bipolar disorder than were teens who were physically inactive. Stroehle and his group suspect that people prone to bipolar disorder may have a predisposing personality trait to be physically active. Kamm does, too. Moreover, this finding raises a provocative question, he pointed out: Might exercise bring on recurrences of mania or depression in persons who already have the disorder? This possibility “should be explored,” he believes.

On the whole, this large prospective study confirms what other smaller, retrospective studies have found—“that there is a beneficial effect of physical activity on most emotional problems,” Kamm concluded. And since people who start exercise programs often don't maintain them, Kamm has found a simple way to get patients in need of physical activity to get moving. He asks patients to wear a pedometer each day not only to determine the extent of their physical activity, but to increase it a little each day.

The study was funded by the German Ministry of Research and Technology and the German Research Society.

An abstract of “Physical Activity and Prevalence and Incidence of Mental Disorders in Adolescents and Young Adults” is posted at<http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=1379132&fu...>.▪