To identify the sequence of and latency between initial AU/NU and initial cannabis use (CU). To investigate whether younger age at AU- and NU-onset is associated with any and earlier CU-onset and a higher risk of transition from first CU to CUD, taking into account externalizing disorders (ED) and parental substance use disorders as putative influential factors.
Prospective-longitudinal community study with N = 3021 subjects (baseline age 14-24) and up to four assessment waves over up to ten years with additional direct parental and family history information. Substance use and CUD were assessed with the DSM-IV/M-CIDI.
Most subjects with CU reported AU (99%) and NU (94%). Among users of both substances, 93%reported AU prior to CU (87%for NU). After adjustment for ED and parental substance use disorders younger age at AU-onset was associated with any CU. Younger age at NU-onset was associated with earlier CU initiation. Younger age at AU- and NU-onset was not associated with a higher risk of CUD.
The cross-substance relevance of younger age at first AU and NU for the risk of CUD is limited to early CU involvement.