Adherence to Australian diet, physical activity and alcohol guidelines is associated with lower risk of depression and anxiety: a secondary analysis of the CALM trial.

While healthy lifestyle behaviours are linked to better mental health, our understanding of how adherence to national recommendations affects outcomes is limited. This study investigates the relationship between adherence to Australian diet, physical activity, alcohol, and smoking guidelines and mental health outcomes in 182 adults experiencing psychological distress. By pooling data from both arms of a non-inferiority trial comparing lifestyle-based therapy to psychotherapy, we examined how adherence to national lifestyle guidelines and dietary components was associated with depression and anxiety outcomes. Greater diet quality (RR = 0.93), physical activity (RR = 0.51) and limited alcohol consumption (RR = 0.59) were linked to reduced risk of depression and anxiety, while ultra-processed foods were associated with higher risk (RR = 1.03). These findings highlight the importance of integrating lifestyle modification into mental health prevention and treatment and suggest that prescribing dietary behaviours based on national guidelines may offer practical mental health benefits.