It is important to study associations between externalizing and internalizing problems on the one hand and cannabis use on the other during early adolescence for several reasons. Firstly, early adolescence is a life phase characterised by rapid biological changes and consecutive maturation processes. These developmental processes might increase vulnerability for enduring

effects of external influences like use of cannabis (Schneider, 2008). Secondly, cannabis use usually starts in early adolescence (Monshouwer et al., 2005), possibly because of increases in peer-influenced PARP inhibitor risk-taking behaviours (e.g. Fergusson and Horwood, 1997). So this appears to be the best possible time to collect behavioural data antedating initiation of cannabis use. The study of associations between internalizing and externalizing behaviours and cannabis use during early adolescence may thus help identifying individuals who are at an increased risk for multiple simultaneous problems (e.g. aggression and substance use), which have been associated with the poorest long-term outcomes. At this stage it might still help targeting one of the problems (preferably the one that occurs first in time) in order to prevent other or combined problems. In the present study, we investigated relations between both internalizing and externalizing behaviour problems and cannabis use in a large population sample of young

Z-VAD-FMK in vivo adolescents enrolled in the Tracking Adolescents’ Individual Lives Survey (TRAILS, Huisman et al., 2008). Using path analysis, we investigated the temporal order of the association between cannabis use and internalizing and externalizing behaviour, thereby controlling for confounding factors to eliminate, to some extent, the effect of shared causes.

It was expected that the link between internalizing behaviour and cannabis use would be weaker than the association between externalizing behaviour and cannabis use. In addition, based on findings to date, it was expected that internalizing and externalizing behaviour problems would precede cannabis use and not the other way Bay 11-7085 around. Data were gathered from participants in the Tracking Adolescents’ Individual Lives Survey (TRAILS), a prospective cohort study among adolescents in the general Dutch population. TRAILS investigates the development of mental and physical health from preadolescence into adulthood (de Winter et al., 2005). The study covers biological, psychological and sociological topics and collects data from multiple informants. Participants come from five municipalities, including both urban and rural areas, in the North of the Netherlands. So far, three data collection waves have been completed: T1 (2001–2002), T2 (2003–2004) and T3 (2005–2007). Participants will be followed until (at least) the age of 24. Of all individuals asked to participate in TRAILS (N = 2935), 76,0% agreed to participate at T1 (N = 2230; mean age 11.09 years; SD 0.55; 50.8% girls). At T2, 96.