Age-related declines in abstract reasoning skills can predict worsening symptoms of depression in later years, according to a new study of Scottish older adults published in the journal Psychological Science.

Previous research has shown that cognitive impairments and depression are often linked in older adults. In general, as cognitive abilities decline, depressive symptoms tend to increase.

But researchers have been unable to conclusively identify the direction of causation. In other words, does cognitive decline lead to depression, does depression lead to cognitive decline, or do they mutually reinforce each other?

To find out, the researchers looked at data collected as part of the Lothian Birth Cohort 1936, a longitudinal study of adults in Scotland. Their analyses included data from 1,091 adults who were evaluated at age 70 and up to three additional times in roughly 3-year intervals until age 79.

Although other research has looked at depression risk in relation to memory deficits and other cognitive impairments tied to Alzheimer’s disease and dementia, the researchers in this study chose to evaluate participants’ abstract reasoning, a cognitive ability closely related to functioning in daily life.

Study participants completed several measures of abstract reasoning, performing tasks such as identifying missing elements from geometric patterns and reproducing visuospatial models using component parts. They also provided information about their depressive symptoms via the Hospital Anxiety and Depression Scale.

On average, abstract reasoning abilities and depressive symptoms worsened among participants over time. In addition, relatively lower cognitive function at each evaluation was tied to subsequent increases in depressive symptoms, and this link continued to get stronger.

The research team used advanced statistical models to study the dynamic relationship between these two measures over time. They discovered that lower abstract reasoning scores at one assessment were associated with greater depressive symptoms at later assessments; however, increased depressive symptoms at a given assessment were not linked to later changes in abstract reasoning.

Sociodemographic and other health-related factors — such as education level, socioeconomic status, and diagnoses related to cardiovascular disease, stroke, and diabetes — did not appear to influence the association between abstract reasoning and depressive symptoms.

Understanding the reason why age-related reductions in abstract reasoning lead to increased depressive symptoms remains a question for future research. The research team notes that there are several possible mechanisms that could be at play, including unmeasured disease processes, genetic susceptibility, and declines in daily functioning.

“Mental health in later life is a topic of increasing importance given aging populations worldwide,” said researcher Stephen Aichele, Ph.D., of the University of Geneva in Switzerland.

“Our findings suggest that monitoring for cognitive decrements in later adulthood may expedite efforts to reduce associated increases in depression risk.”

Source: Association for Psychological Science