Elucidating the association between depression, anxiety, and cognition in middle-aged adults: Application of dimensional and categorical approaches

Background: In older adults, depressive and anxiety symptoms are associated with dementia risk, and represent a manifestation of the dementia prodrome. Understanding how these symptoms are related to cognition in midlife may inform risk models of dementia. Methods: This study examined the relationship between depressive and anxiety symptoms, and cognition, in a sample (n= 2,657) of participants enrolled in the Healthy Brain Project. Depressive and Anxiety symptoms were assessed using the Depression Anxiety and Stress Scale, Hospital Anxiety and Depression Scale, and centre for Epidemiological Studies Depression Scale. Objective cognition was assessed using the Cogstate Brief Battery and subjective cognition assessed using the Alzheimer's disease Cooperative Study Cognitive Function Instrument. Results: Somatic- and panic-related anxiety symptoms were associated significantly with poorer attention; while tension- and panic-related anxiety were associated significantly with poorer memory. Having clinically meaningful anxiety or depressive symptoms was associated with increased subjective cognitive concerns (d=-0.37). This was further increased for those with clinically meaningful anxiety and depressive symptoms (d = -1.07). Limitations: This study reports cross-sectional data, and uses a sample enriched with individuals with a family history of dementia who are therefore at a higher risk of developing dementia compared to the general population. Additionally, biological markers such as cortisol, Aβ, and tau were unavailable. Conclusion: The results support the hypothesis that depressive and anxiety symptoms may increase risk of cognitive decline. Further, they suggest that using depression and anxiety as clinical markers may be helpful in identifying the earliest signs of cognitive decline.