Cognitive impairment is often comorbid with depression and anxiety, and the cognitive status of older adult patients can drastically impact depression treatment outcomes. The cognitive status of these patients invariably changes psychological treatment approaches that otherwise are viable and feasible in older adults. For example, although cognitive behavioral therapy is effective in treating cognitively intact patients with depression, it often relies on executive function (such as flexible thinking and problem solving) and other cognitive abilities that are impaired in patients with comorbid cognitive impairment. Practically, this results in unstandardized modifications to psychotherapy that may impact the fidelity—and thus effectiveness—of treatment. It is important to assess and classify cognitive dysfunction in depression treatment-seeking older adults in trials. This can help generalize research findings and identify potential barriers in transferring psychotherapeutic approaches for older adults with depression from treatment trials to practical clinical use, particularly in hard-to-treat populations with comorbid cognitive impairment.

A systematic literature search was conducted in PubMed for the period 2000-2022. Study inclusion criteria was operationalised as follows: participants were identified as older adults (55 years and older), their primary psychiatric diagnosis was depression, and the study was a trial for depression treatment. Key search terms included: depression, treatment, psychotherapy, therapy, counseling, intervention, older adult, senior, late-life, elder, aged, clinical trial, and randomized controlled trial.

An initial search of the key terms returned 3,972 articles. 178 of these articles were subject to full text review. Of those, 45 articles met inclusion criteria. Overall study quality was acceptable. A portion of treatment trials did not assess for cognitive functioning. A majority of the articles excluded patients with cognitive impairment, with no further elaboration on the potential impact of cognitive functioning on treatment outcomes. A smaller portion of studies were more inclusive of the cognitive range of patient participants; however, they did not comment on the cognitive heterogeneity of their samples. Only three studies used a more extensive neuropsychological battery to examine cognitive profiles of patient participants. However, two of these studies also excluded individuals that fell below the cognitively intact range based on brief cognitive screening measures. Of the few studies that examined depression treatment in cognitively impaired and dementia patient populations, two trials examined cognitive functioning as a predictor or moderator of depression treatment outcome.

Given that cognitive status can significantly impact depression treatment outcomes for older adults, there is a shocking dearth of inclusion of cognitively impaired patients in depression treatment clinical trials. Moreover, the limited studies that examined depression treatment in cognitively impaired populations, there is a lack of comprehensive cognitive assessment, and lack of exploration on how different types of cognitive dysfunction may contribute to variable depression treatment response. Future depression treatment trials in older adults should expand to include a variety of cognitive functioning ranges, as well as a more detailed assessment of how specific cognitive domains may impact treatment outcomes.