Aims. To identify early onset cannabis users by measuring basal hypothalamic–pituitary–adrenal (HPA) axis activity, which may be a risk factor for early onset substance use when showing low activity. Design. In a prospective cohort study, adolescents who initiated cannabis use at an early age (9–12 years), those who initiated at a later age (13– 14 years) and those who did not use cannabis by the age of 14 were compared with respect to HPA axis activity. Setting and participants. Data were used from the first and second assessment wave of the TRacking Adolescents’ Individual Lives Survey (TRAILS), that included 1768 Dutch young adolescents aged 10–12 years who were followed up across a period of 2 years. Measurements Cortisol was measured in saliva samples at awakening, 30 minutes later and at 8 p.m. at age 10–12. Self-reported age at first cannabis use was used. Findings. The early onset group had lower cortisol levels 30 minutes after awakening than the late onset group (OR=0.93, 95% CI: 0.86–0.99). Furthermore, compared to non-users, the early and late onset cannabis users had higher levels of cortisol at 8 p.m. (OR=1.25, 95% CI: 1.03–1.53 and OR=1.21, 95% CI: 1.01–1.45, respectively). Conclusions. Some evidence was found for HPA axis hypo-activity at awakening in adolescents with early onset of cannabis use compared to late onset users, which might indicate an increased risk for early onset users of seeking stimulation to restore arousal levels by using substances.