A Latent Class Analysis of Age at Substance Use Initiation in Young Adults and its Association with Mental Health

This study aims to identify empirically-driven classes of age-of-onset across multiple substances (alcohol, tobacco, cannabis) and to characterize the different classes in relation to mental health and substance use severity. The sample comprised 1,051 young adults (aged 18–25; 61.9% women), recruited from universities and vocational schools in Spain, who reported lifetime alcohol, tobacco and cannabis use. Participants were asked to complete questionnaires about demographics, substance use and mental health. A latent class analysis (LCA) was conducted using the age of onset of alcohol, tobacco, and cannabis use as an indicator. Three distinct classes were identified: C1 (45%), characterized by early alcohol and late cannabis and tobacco use; C2 (49.1%) presenting early alcohol, cannabis and tobacco use; and C3 (5.9%) showing late alcohol, cannabis, and tobacco use. Classes 1 and 2 exhibited the poorest psychosocial functioning, and Class 2 showed the highest levels of impulsivity traits. There were within-class sex differences, which suggested poorer mental health in females. The findings support the idea that early-onset use of the three substances is common and that this pattern is associated with increased involvement in substance use and poor mental health.