R. de Graaf
It was answered with a three-year prospective cohort of 600 young adults (18-30 years) who used cannabis frequently (≥3 days weekly for >1 year), distinguishing users with and without dependence; comparisons with non-users and patients in treatment; and ‘naturalistic’ measurements of cannabis use.
1. The three-year course of cannabis use and dependence was dynamic. Overall, cannabis use decreased; "only" 37% of frequent users developed dependence; and "only" 28% of dependent users remained dependent.
2. For the presence, onset and persistence of cannabis dependence, the role of THC exposure (frequency, quantity, potency) seemed small. Instead, current (mental health) problems and previous cannabis abuse/dependence symptoms were important.
3. Frequent cannabis users fulfilling criteria for cannabis dependence showed high remission rates without treatment, no perceived need for treatment, and better functioning, mental health and less cannabis use than patients in treatment.
As in this study THC exposure played a small role in the course of cannabis use, it seems unlikely that a decrease of the THC concentration will considerably reduce the incidence of cannabis dependence and treatment demand. Selective (low threshold) prevention seems more promising as some would benefit from being convinced to seek treatment. Still, the many (frequent) cannabis users fulfilling criteria for dependence who are not in treatment, labelled the "treatment gap", may be less problematic than previously assumed.
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