Since the survival mixture analysis showed a different structure of risk of initiation across substances, a latent class analysis focusing on the users only was also examined. Importantly, the latent class analysis distinguished groups that were clearly ordered with respect to age of onset. Furthermore, within the early onset class, inhalants had the lowest mean age of first use, whereas for instance “other substances” were initiated at a significantly later mean age. This pattern of first use is likely related to accessibility of different substances, which has been shown to be an important predictor of substance use (Gillespie et al. 2011).
