Differential responses to cannabis potency: a typology of users based on self-reported consumption behaviour.

AIMS: To determine whether a classification of cannabis users into different types can help to clarify the relationship between cannabis potency and consumption behaviour, harmful physical effects and psychological dependency.

METHODS: A field sample of 388 respondents was recruited who had smoked cannabis at least once in the past month. They were contacted and interviewed in 28 cannabis coffee shops located in five Dutch cities. Data were collected with an assisted self-completion questionnaire. Cluster analysis was performed using the k-means method.

FINDINGS: Various ways were observed in which cannabis users in natural settings adjusted their intake to the potency of the drug. Cluster analysis identified three broad types of cannabis users. The strongest high type was the youngest, consumed the highest monthly dose, inhaled higher-potency cannabis more deeply, and scored highest on psychological cannabis dependency. The consistent high type preferred milder cannabis, consumed the lowest monthly dose, and compensated for stronger cannabis by inhaling less deeply and smoking less. The steady quantity type was the oldest, usually smoked alone, consumed an intermediate monthly dose, and did not tend to adjust the depth of inhalation to the potency of the cannabis. The results suggest that this typology might also reflect three successive stages in the careers of continuing cannabis users.

CONCLUSIONS: Laboratory studies to assess the effects of higher THC concentrations on external and internal exposure to cannabis should allow for the possibility that the types of users studied can affect the results.