Generational effects in self-reported age of onset for youth suicidal ideation, self-harm and attempted suicide: A retrospective analysis using data from the Australian National Study of Mental Health and Wellbeing, 2020–2022

OBJECTIVE: The onset of youth suicidal ideation and behaviour is a critical predictor of future mental health. This study examines generational differences in the prevalence and age of onset for suicidal ideation, plans, self-harm, and suicide attempts by age 25 in a nationally representative Australian cohort. METHOD: (16-25 years), Millennials (26-41 years), Generation X (42-57 years), and Baby Boomers (58-76 years). Cox proportional hazards models assessed the impact of demographic, childhood adversities, and mental health factors across generations. RESULTS: Of the 14,753 respondents, 16.1% were Generation Z, 31.3% Millennials, and around one-quarter were from either Generation X or the Baby Boomer generation. Generation Z had the highest hazards for youth suicidal ideation, planning, self-harm, and suicide attempts, with the youngest age of onset. Adverse childhood experiences and lifetime mental health diagnoses were consistent risk factors across generations, but generational differences in their impact were evident. Sexual abuse before 19 was less strongly associated with earlier onset in Generation Z, while witnessing parental violence and exposure to suicide in others had stronger associations with younger onset in Generation Z. Mental disorders were linked to earlier onset, particularly in Baby Boomers. CONCLUSIONS: Generational differences in the prevalence and age of onset of suicidal ideation and behaviours in Australia are evident, emphasising the need for a tailored, multi-sectorial suicide prevention strategy to address these evolving risks.