Cannabis changes: Understanding dynamics of use and dependence

Cannabis is the most widely used illicit drug. Part of ever-users become frequent users and continue to use over a longer period. 600 frequent users (18-30 years) were enrolled in a 3-year longitudinal study. Trajectories of frequent cannabis use and cannabis dependence appeared very dynamic. Overall use and dependence declined over time. The empirical core of this thesis was an in-depth qualitative analysis of the trajectories of a sub-sample of 47 participants. Taking a life course perspective as a main theoretical framework, the leading questions were: How and why do frequent young adult users increase, decrease or quit their use over time? And why do some develop or recover from dependence and others do not? The dynamics in frequent cannabis use and cannabis dependence were examined, particularly the underlying processes and mechanisms. In general, participants lived a life rather similar to other young adults. Cannabis use appeared predominantly a leisure activity. This thesis uncovered the reciprocal relationships and mechanisms involved in cannabis trajectories. Social relationships (particularly peers and partners) were of great importance in these trajectories, including in processes of desistance from and persistence of use. Even when similar, social relationships, work and study, leisure and related life events had different meanings for individuals. Meaning-giving to life events was essential. Agency was a necessary ingredient for desistance and played a key role in life events becoming turning points in cannabis trajectories. Like many other aspects in life, over time, either gradually or abruptly, cannabis use and dependence can change.