Peers are a risk factor in the development of addiction because they act as influential models by introducing, providing, or pressuring risky activities, such as drug or alcohol use. Findings from a national drug agency (AADK) study conducted in Malaysia showed that of 26,841 drug addicts surveyed between 2007 and 2008, 55% became addicted after being introduced to the substance by friends. Social identity theory (Tajfel and Turner, 1986) suggests that peers are highly influential because people want to belong to an ‘in-group’ (the group with which they identify) in order to be socially accepted and this means they are more likely to adopt in-group behaviours. Morgan & Grube (1991) showed that peers affected both the initiation and maintenance of smoking and Morton et al. (2005) found that adolescents who spent more time with deviant peers were more likely to drink alcohol.