Depression is associated with incidence and worsening of an array of comorbid conditions; however, it is unclear if treating major depressive disorder (MDD) improves incidence risk or severity of comorbid diseases. A systematic review of randomized controlled trials (RCTs) and meta/pooled analyses of RCTs evaluated whether significant improvement of depression following antidepressant treatment (psychotherapy and/or pharmacotherapy) corresponded with improvement of comorbidity outcomes. Thirty studies, including 24 RCTs (n=6,333) and 6 meta-analyses or pooled analyses of RCTs were included in the review. Most studies were under one year in duration and all were conducted in the United States or Europe. Studies were required to report a statistically significant improvement in depression scores in order to be included.
The review found that an improvement in depression did not correspond with improvement in comorbid Alzheimer’s disease or cancer outcomes; however, improvement in Parkinson’s disease, multiple sclerosis, and chronic obstructive pulmonary disease (COPD) outcomes were identified. Mixed findings were found for comorbid outcomes in the following: cardiovascular disease (CVD), diabetes, substance abuse, and pain conditions. In the case of CVD, improvement of depression was associated with a decrease in the risk of CVD events in otherwise healthy individuals and the risk of cardiac symptoms (but not events) in people with prior cardiac hospitalizations. Improvement of depression following treatment was associated with improvement in diabetes pain and symptom severity, but not glycemic control outcomes. Several, but not all, studies reported decreases in alcohol and substance use alongside improvement in depression symptoms. Additionally, pain symptoms improved for some pain conditions (backache, headache, fibromyalgia), but not others (chronic pain). See Figure 1 for a broad summary of the outcomes. These findings should be interpreted with caution due to the wide variety of study designs and generally small effect sizes reported by the reviewed studies. However, this systematic review suggests that appropriate treatment of MDD may additionally improve outcomes of some comorbid conditions.
Figure 1. Summary of comorbidity outcomes in patients with improvement in depression symptoms following antidepressant treatment, including pharmacotherapy and psychotherapy.
Arnaud AM et al. Prim Care Companion CNS Disord 2023;25(1):22r03330. Abstract.
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