The relationship between methamphetamine use and violent behaviour

The current bulletin assesses whether there is any relationship between the increasing assault rate in NSW seen over the past decade and increasing methamphetamine use. During this time, there have been several changes to methamphetamine use patterns that could have contributed to an increase in methamphetaminerelated problems, such as violent behaviour. There is currently insufficient evidence to infer a direct causal link between methamphetamine use and violence, but there is considerable evidence that the two entities are related. The strongest evidence for a relationship between methamphetamine use and violence is in the context of methamphetamine-induced psychosis. In this context, violence is likely to be related to persecutory delusions and perceived threat. There is also experimental evidence that chronic use of the drug increases the risk of violent behaviour, and a proportion of chronic methamphetamine users report problems controlling violent behaviour. Despite this evidence, it is not clear whether violent behaviour among chronic methamphetamine users is due to methamphetamine use per se or co-occurring factors (e.g. alcohol use, psychiatric status, personality, lifestyle associated with illicit drug use). Acute intoxication with methamphetamine alone does not appear to lead to violent behaviour, but it may enhance aggression in someone who is otherwise provoked. In conclusion, there is currently insufficient empirical data to estimate whether, or to what extent, methamphetamine use has increased assaults in NSW. Existing evidence suggests that methamphetamine use is likely to have a relatively minor impact on the assault rate in NSW in comparison with other factors.