Exercise in adulthood was associated with an almost 20% reduction in the odds of having depressive symptoms, according to a study published online Oct. 15 in JAMA Psychiatry. Conversely, the presence of depressive symptoms was found to be a barrier to increased physical activity.
Snehal M. Pinto Pereira, Ph.D., and her colleagues reported that adults who were physically active at age 23 years tended to experience fewer depressive symptoms as they aged, while those who engaged in less physical activity at that age were more likely to see their depressive symptoms increase throughout adulthood (JAMA Psychiatry 2014 Oct. 15 [doi:10.1001/jamapsychiatry.2014.1240]).
By analyzing data on depressive symptoms and physical activity frequency collected at ages 23, 33, 42, or 50 years in a British cohort study of 11,000 adults born during the same week in 1958, Dr. Pinto Pereira and her colleagues found a bidirectional effect between exercise and depression.
“At most ages, we found a trend of fewer depressive symptoms with more frequent activity,” wrote Dr. Pinto Pereira of the Population, Policy, and Practice program at the University College of London Institute of Child Health and her colleagues.
The more physical activity per week, the lower the mean number of depressive symptoms a person experienced by age 50 years (0.06; 95% confidence interval, –0.09 to –0.04), and the magnitude of association did not vary with age (P = .21).
If a person was inactive at 23 years of age and remained inactive 5 years later, there was no change in symptom level (mean difference, –0.01; 95% CI, –0.04 to 0.02). However, if the person increased physical activity to three times a week, there was a lower mean number of depressive symptoms (mean difference, −0.18; 95% CI, −0.22 to −0.15). Although the investigators noted that these differences equaled an estimated reduction for the odds of being depressed by as much as 19%, the relationship between symptoms and activity was seen to weaken with age (P < .001).
The average level of physical activity in asymptomatic adults at 23 years was higher 5 years later by 0.60 (95% CI, 0.57-0.64) times per week, whereas it was lower at 0.53 (95% CI, 0.49-0.56) times per week in the same age group 5 years later if the person had one additional depressive symptom. The frequency of physical activity did not differ in asymptomatic adults at 43 years who subsequently had zero or one symptom at age 48 years.
The results were based on self-reported data as analyzed with the psychological subscale of the Malaise Inventory, which cannot fully prevent confounding factors, such as misreported body mass index measurements. Still, Dr. Pinto Pereira and her colleagues wrote, their study indicated “activity may alleviate depressive symptoms in the general population and, in turn, depressive symptoms in early adulthood may be a barrier to activity.”
This study was supported by the Department of Health Policy Research Programme through the Public Health Research Consortium, United Kingdom. The authors reported no conflict of interest.
On Twitter @whitneymcknight