||During early adolescence, there is no association between internalizing behaviour and cannabis use. There is an association between externalizing behaviour and cannabis use, where externalizing behaviour precedes cannabis use rather than the other way around. Secondly, during adolescence, there is an association between psychosis vulnerability and cannabis use, where cannabis use predicts psychosis vulnerability and vice versa, suggesting a bi-directional cascading association. Thirdly, during early adolescence, the social skill “self-control” was (unexpectedly) unrelated to cannabis use. Cooperation and assertiveness are associated with cannabis use during this life phase, where higher levels of cooperation decrease the chance of using cannabis and higher levels of assertiveness increase the chance of using cannabis during early adolescence. Cooperation and assertiveness did not differentiate between early and late onset of cannabis use or predict frequency of use. In addition, compared to non-users, cannabis users experience problems only in motivational inhibitory control, not in cognitive inhibitory control. Also, cannabis users experience problems in behavioural impulsivity, which is related to motivational inhibitory control. Lastly, cannabis users have problems with social perception in comparison to non-using controls, particularly when these social perception skills involve emotion recognition. Also, heavy cannabis users experience significantly more psychological problems when they have relatively poor social perception skills. Future research must determine whether the behavioural and cognitive concepts and constructs examined in this thesis in relation to cannabis use should be incorporated in prevention and intervention programs.