The association of environmentally sustainable healthy dietary patterns and risk of neurological and psychiatric disorders: A systematic review and meta-analysis of 28 cohorts

The current burden of neurological and psychiatric disorders is a major issue in public health. We aimed to explore how adherence to healthy diets with low environmental impact (HDLE)—Mediterranean, EAT-Lancet and Healthy Provegetarian diets—are associated with neurological and psychiatric outcomes (depression, anxiety, cognitive impairment, and dementia) in prospective cohort studies of adults. We systematically searched four databases until March 2025. Pooled risk ratios (pRRs) with 95% confidence intervals (CIs) along with prediction intervals (PIs) were estimated. Our meta-analyses compared the incidence of mental outcomes between individuals with the highest vs. lowest (reference category=1) adherence to HDLE. The certainty of evidence was assessed with the GRADE framework. This systematic review included 39 articles involving 472,125 adults (mean age 63y,52% female) from 28 unique cohorts with a mean follow-up of 10y. The highest (vs. the lowest) adherence to HDLE was associated with a lower risk of depression (pRR: 0.80;95%CI:0.75–0.85;PI:0.68–0.93;k=12/n=333,218), cognitive impairment (pRR:0.66;95%CI:0.60–0.72;PI:0.57–0.76;k=5;n=27,338), and dementia (pRR: 0.87;95%CI:0.76–0.99;PI:0.63–1.20; k=11/n=235,863). A meta-analysis for incident anxiety was not conducted due to the scarcity of studies (k=2). Certainty of evidence was rated as low for depression and very low for cognitive impairment and dementia. A higher adherence to HDLE was associated with a lower risk of depression (20%), cognitive impairment (34%) and dementia (13%). • Higher adherence to healthy diets with low environmental impact was associated with a 20% lower risk of depression, a 34% lower risk of cognitive impairment, and a 13% lower risk of dementia in adults, based on data from 39 studies across 28 unique cohorts. • The meta-analyses included 472,125 adults with an average follow-up of 10 years. • Most studies were conducted on European cohorts, using the Mediterranean diet and exploring depression risk. • Certainty of evidence was rated as low for depression and very low for cognitive impairment and dementia; results should be interpreted with caution. • Limited data for anxiety impede us from conducting a meta-analysis.