Vigorous exercise associated with mental illness vulnerability

By Mark Cowen, Senior medwireNews Reporter

Contrary to expectations, engagement in vigorous exercise is positively associated with the incidence and prevalence of psychiatric disorders, particularly bipolar II disorder and alcohol dependence, US researchers report.

In a study of data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), the team found that individuals who engaged in vigorous physical exercise were significantly more likely to be diagnosed with a psychiatric disorder, less likely to achieve remission, and more likely to relapse than nonexercisers.

"This surprising finding may be due to reward-related factors that influence both exercise engagement and the expression of certain psychiatric disorders," suggest Elias Dakwar (Columbia University, New York) and team in the Journal of Clinical Psychiatry.

The researchers studied data from a nationally-representative sample of 23,505 adults who participated in two waves of NESARC assessments conducted in 2001-2002 (wave 1) and 2004-2005 (wave 2).

Information regarding psychiatric diagnoses and sociodemographic factors was collected at both waves, while information regarding the frequency and duration of vigorous exercise over the past 12 months was collected at wave 2.

Vigorous exercise was defined as engaging in strenuous physical activity for 20 minutes or more at least 3 days a week, as recommended by American College of Sports Medicine guidelines.

The researchers found that, compared with participants who reported never exercising, those who engaged in vigorous exercise were significantly more likely to be diagnosed with any Axis I disorder, at an adjusted odds ratio (OR) of 1.22.

The specific disorders accounting for this association were bipolar II disorder (OR=2.29), alcohol dependence (OR=1.35), and nicotine dependence (OR=1.13).

Among participants with a psychiatric disorder at wave 1, those who engaged in vigorous exercise were significantly less likely than nonexercisers to achieve remission between waves (OR=0.77).

In addition, vigorous exercisers were significantly more likely to be diagnosed with a psychiatric disorder between waves 1 and 2 than nonexercisers (OR=1.15).

Dakwar et al conclude: "This investigation suggests that the pursuit of vigorous exercise is associated with a vulnerability to mental illness."

"Even though our findings run counter to some prevailing assumptions regarding exercise and mental health, they can be interpreted to give support to the hypothesis that exercise can serve as a reward that is particularly reinforced in individuals who have vulnerabilities in reward-related neurocircuitry."

They add: "Prospective trials will be helpful in further clarifying the associations between exercise and mental illness, as the relationships between the two are more complex than previously believed."

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