Are diagnostic orphans at risk of developing cannabis abuse or dependence? Four-year follow-up of young adult cannabis users not meeting diagnostic criteria.

OBJECTIVE: To examine the characteristics of "diagnostic orphans" among cannabis users - those who report one or two symptoms of DSM-IV dependence but do not meet diagnostic criteria for DSM-IV abuse or dependence - 4 years post-assessment.
METHOD: Data were collected from a representative population cohort of young Australian adults. Those who reported that they had used cannabis at least weekly at some point within the past year were assessed for symptoms of DSM-IV cannabis abuse and dependence using the Composite International Diagnostic Interview at age 20-21 years. The entire sample was followed up 4 years later. At age 24-25 years, cannabis use and cannabis diagnostic category were examined according to diagnostic category at age 20-21 years.
RESULTS: Diagnostic orphans at age 20-21 years were more likely than non-problem cannabis users at that age to be using cannabis, and to meet criteria for cannabis abuse or dependence 4 years later. Those who had met criteria for cannabis abuse or dependence, however, appeared to be at greater risk relative to non-problematic users and diagnostic orphans of meeting criteria for cannabis abuse and dependence at follow-up.
CONCLUSIONS: Young adult diagnostic orphans for cannabis use appear to be at lower risk of meeting full (or partial) diagnostic criteria after a 4-year follow-up, compared to those who had met criteria for cannabis abuse or dependence. This suggests that there is prognostic diagnostic utility in the threshold for dependence symptoms among young adult cannabis users. Diagnostic orphans did appear to be at greater risk than non-problem users for developing dependent and daily cannabis use, however, suggesting that clinicians would do well to intervene with this group.