Abstract
Lifestyle interventions encompass educational and treatment components addressing health risk behaviours such as sedentary lifestyles, nutrition, tobacco use, alcohol and drug use, sleep hygiene, and sexual health behaviours, and are known to improve symptoms of mental illness. However, these interventions are not widely available to young adults. The aims of this study were to (1) determine the proportion of young adults with mental illness who would benefit from lifestyle interventions and (2) describe the benefits and operational factors that should be considered when planning lifestyle interventions for young adults. A two-stage approach was utilised, including structured consultation with experts in youth mental health (n = 12) and an online Delphi study with respondents with expertise and interest in lifestyle interventions (n = 14). The recommended proportion of young adults benefiting from lifestyle interventions varied between the structured consultation and Delphi study. Generally, the proportion increased with illness severity. Overall, study participants recommended that more young adults should have access to individually delivered interventions compared to group interventions. This study provides provisional estimates and operational details that could be used to increase the availability of lifestyle interventions for young adults, improving mental health, functioning, and physical health, and supporting improved life outcomes.