Dr. Christina S. Dintica
Previous research suggests a possible link between depression and increased risk of dementia in older adults, but the association between depression and brain health in early adulthood and midlife has not been well studied, wrote Christina S. Dintica, PhD, of the University of California, San Francisco, and colleagues.
In a study published in the Journal of Affective Disorders, the researchers identified 649 individuals aged 23-36 at baseline who were part of the Coronary Artery Risk Development in Young Adults (CARDIA) study. All participants underwent brain MRI and cognitive testing. Depressive symptoms were assessed six times over a 25-year period using the Center for Epidemiological Studies Depression scale (CES–D), and the scores were analyzed as time-weighted averages (TWA). Elevated depressive symptoms were defined as CES-D scores of 16 or higher. Brain age was assessed via high-dimensional neuroimaging. Approximately half of the participants were female, and half were Black.
Overall, each 5-point increment in TWA depression symptoms over 25 years was associated with a 1-year increase in brain age, and individuals with elevated TWA depression averaged a 3-year increase in brain age compared with those with lower levels of depression after controlling for factors including chronological age, sex, education, race, MRI scanning site, and intracranial volume, they said. The association was attenuated in a model controlling for antidepressant use, and further attenuated after adjusting for smoking, alcohol consumption, income, body mass index, diabetes, and physical exercise.
The researchers also investigated the impact of the age period of elevated depressive symptoms on brain age. Compared with low depressive symptoms, elevated TWA CES-D at ages 30-39 years, 40-49 years, and 50-59 years was associated with increased brain ages of 2.43, 3.19, and 1.82.
In addition, elevated depressive symptoms were associated with a threefold increase in the odds of poor cognitive function at midlife (odds ratio, 3.30), although these odds were reduced after adjusting for use of antidepressants (OR, 1.47).
The mechanisms of action for the link between depression and accelerated brain aging remains uncertain, the researchers wrote in their discussion. “Studies over the last 20 years have demonstrated that increased inflammation and hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis are two of the most consistent biological findings in major depression, which have been linked to premature aging,” they noted. “Alternative explanations for the link between depression and adverse brain health could be underlying factors that explain both outcomes rather independently, such as low socioeconomic status, childhood maltreatment, or shared genetic effects,” they added.
Adjustment for antidepressant use had little effect overall on the association between depressive symptom severity and brain age, they said.
The current study findings were limited by the single assessment of brain age, which prevented evaluation of the temporality of the association between brain aging and depression, the researchers noted.
However, the results were strengthened by the large and diverse cohort, long-term follow-up, and use of high-dimensional neuroimaging, they said. Longitudinal studies are needed to explore mechanisms of action and the potential benefits of antidepressants, they added.
In the meantime, monitoring and treating depressive symptoms in young adults may help promote brain health in midlife and older age, they concluded.
The CARDIA study was supported by the National Heart, Lung, and Blood Institute, the National Institute on Aging, and the Alzheimer’s Association. The researchers had no financial conflicts to disclose.