When reaching their early twenties, almost 60% of the participants of the contemporary Dutch TRAILS and ALSPAC study confirm to have used cannabis at some point in their life, one in five has used ecstasy, and around one in ten young adults has used amphetamines, cocaine, or magic mushrooms. Given the adverse effects of adolescent drug use on adult outcomes, these numbers are alarming. Why do so many young people experiment with drugs? How many of them are regular users? Is the use of illicit drugs systematically linked to alcohol and tobacco use? How are temporary and chronic use reflected in psychosocial adjustment and accomplishment of normative development milestones? Perhaps most pressing, can we identify protective factors that increase the likelihood for youngsters to abstain and users to desist from using drugs before they can leave lasting damage? Answering those questions is crucial to understand drug use pathways and their antecedents and outcomes, through the life course.
Focussing on incidence and course of illegal drug use throughout adolescence and young adulthood, we aim to a) identify predictors of onset of experimental and regular use of cannabis and hard drugs, b) predict the developmental trajectories of cannabis and hard drug use, and c) identify outcomes of these trajectories. Cannabis and hard drug use are no isolated phenomena, they occur in interplay with use of other substances such as tobacco and alcohol use and are often connected to mental health problems from the internalizing and externalizing spectrum. Hence, co-developmental pattern and interactive and cumulative risks are identified.
Two major multi-reporter longitudinal cohort studies provide the data for this project: The British Avon Longitudinal Study of Parents and Children (ALSPAC, http://www.bristol.ac.uk/alspac/) is an ongoing study of 14.500 families where the first assessment took part during pregnancy and the target sample of young people has now reached the mid-twenties. Repeated measures of dDrug use have been collected xx times s been assessedon an annual or semi-annual basis from age 10 [link to questionnaires][how often] using [instrument]. Extensive contemporaneous information is available including on early life, family adversity, social position, neighbourhood, school, temperament, externalising and internalising problems, and peer drug use[covariate, risk, protective factors] are available. The Dutch TRacking Adolescents’ Individual Lives Survey (TRAILS, www.trails.nl/en/) is an ongoing study of 2261 individuals who were recruited into the study at age 11 and are now also in their mid-twenties. Drug use has been assessed [how often] using [instrument]. Extensive information on [covariate, risk, protective factors] are available. The liberal Dutch climate towards drug use, specifically the tolerance policy towards cannabis possession and production is in stark contrast to the British perspective where cannabis is criminalized. By comparing two cohorts of equal age, we are able to identify the role of the cultural context, a thus far severely under-researched aspect.