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

While healthy lifestyle behaviours such as eating a high-quality diet are strongly linked to better mental health, our understanding of how adherence to specific national recommendations in at-risk populations can affect mental health outcomes is limited. This study investigates the relationship between adherence to the Australian diet, physical activity, alcohol use, and smoking guidelines and mental health outcomes in 182 adults experiencing psychological distress. By pooling data from both arms of the CALM trial, a non-inferiority study comparing lifestyle-based therapy to psychotherapy, we examined how adherence to national lifestyle guidelines and specific dietary components over eight weeks was associated with depression and anxiety outcomes. Higher diet quality (RR: 0.93; 0.91), greater physical activity (RR: 0.51; 0.63) and limiting alcohol consumption (RR: 0.59; 0.63) according to guidelines was linked to reduced risk of depression (PHQ-9) and anxiety (GAD-7) respectively, while increased intake of ultra-processed foods was associated with higher risk (RR:1.03; 1.23). Notably, the impact of intake of certain nutrients, such as fibre and omega-6 fatty acids, differed between depression and anxiety outcomes. These findings highlight the importance of integrating lifestyle modification into mental health prevention and treatment strategies and suggest that prescribing dietary behaviours based on national guidelines may offer practical mental health benefits.