The Relationship Between Combined Lifestyle Behaviors and Mental Illness in Emerging Adults: A Narrative Review

Emerging adults (18-25 years) experience the highest prevalence of mental illness, including anxiety and depression, affecting more than 11 million individuals in the United States. Traditional treatment approaches, such as psychotherapy and pharmacotherapy, may not fully address the complex and interrelated risk factors unique to emerging adults. Targeting lifestyle behaviors, including diet, sleep, physical activity, and substance use, has emerged as a promising adjunctive strategy for the prevention and treatment of mental illness. Growing evidence suggests that these behaviors frequently co-occur and may exert synergistic effects on mental health outcomes. This review synthesizes findings from observational studies and randomized controlled trials examining the relationship between combined lifestyle behaviors and mental illness in emerging adults. A total of 17 studies met inclusion criteria, including 14 observational studies and three intervention trials. Observational findings consistently indicated that lifestyle patterns characterized by a greater number of unhealthy behaviors were associated with higher levels of depression, anxiety, and psychological distress. In contrast, the three intervention studies did not demonstrate significant improvements in mental health outcomes following lifestyle interventions. Overall, the findings suggest a synergistic effect of multiple lifestyle behaviors associated with mental illness in emerging adults. However, substantial heterogeneity in how studies defined and categorized "healthy" versus "unhealthy" behaviors limited cross-study comparisons. This review highlights the need for standardized measurement approaches and more rigorous intervention trials to elucidate the potential synergistic effects of combined lifestyle modifications on mental health outcomes in this population.