Twenty-Five and Up Study: A New Wave of the Brisbane Longitudinal Twin Study

The 25Up study aimed to explore psychological and behavioral risk factors for mental illness by following up on a cohort of Australian twins and their non-twin siblings who had been previously studied from age 12 and in the 19Up study. Conducted between 2016 and 2018, the study involved 2540 participants (59% female), including 341 monozygotic twin pairs, 415 dizygotic twin pairs, and 1028 non-twin siblings and singletons, with a mean age of 29.7 years. The study collected data on 20 mental disorders, demographic information, general and physical health, psychosocial factors, and female health traits. Notably, 86% of participants had been genotyped, allowing for the assessment of epidemiological risk factors and the heritability and genetic correlations of mental conditions. The study's comprehensive data set from the Brisbane Longitudinal Twin Study will facilitate detailed investigations into the genetic pathways underlying psychiatric illnesses.