Mood disorders, particularly depressive and bipolar disorders, have emerged as potentially modifiable risk factors for dementia. However, the burden of dementia attributable to mood disorders remains unquantified. We aimed to quantify that burden among adults aged 45 years and older using a comparative risk assessment approach.

A literature search was performed in PubMed, Embase, and MEDLINE to identify cohort studies that assessed the association between mood disorders and subsequent dementia from database inception to 9th April 2025. Random-effects models were used to derive pooled risk ratios (RRs). Assuming a 5-year lag between mood disorders and dementia onset, we calculated population attributable fractions (PAFs) and age-standardized disability-adjusted life year (DALY) rates (ASDRs) at global, regional, and national levels. Temporal trends in ASDR were analyzed using joinpoint regression to estimate average annual percentage change.

77 articles were included. The pooled RR for all-cause dementia was 1.90 (95% confidence interval [CI]: 1.70, 2.12) for depressive disorders, and 3.10 (95% CI: 2.21, 4.35) for bipolar disorder. For dementia subtypes, depressive disorders showed an association with Alzheimer’s disease (RR: 2.57, 95% CI: 2.05, 3.23), and bipolar disorder was associated with vascular dementia (RR: 3.67, 95% CI: 2.42, 5.57). In 2016, the global PAFs of dementia attributable to depressive disorders were 4.79% (95% CI: 3.19%, 6.58%) in males and 5.56% (95% CI: 3.56%, 7.84%) in females. PAFs for bipolar disorder were 1.22% (95% CI: 0.65%, 2.01%) in males and 1.34% (95% CI: 0.71%, 2.18%) in females. In 2021, the global ASDR of dementia attributable to depressive disorders was 89.61 (95% CI: 34.80, 192.24) per 100,000 population, while the global ASDR for bipolar disorder was 15.91 (95% CI: 5.56, 37.87) per 100,000 population.

Since mood disorders are a substantial contributor to dementia burden, integrating mental health management into public health policies is essential.