The Prognostic value of trait anger in treatment of methamphetamine dependence

Methamphetamine is a potent stimulant with high abuse potential and is the second most widely used illicit drug in the world, after cannabis. The prevalence of methamphetamine use in Australia is among the highest in the world with an estimated 1.1 million people (6% of those aged 14 years and over) reporting lifetime use. Nearly all users of methamphetamine experience withdrawal and aggression is a common sequela. Methamphetamine use is a risk factor for a wide range of negative consequences including physical, neurological and psychiatric illness, property crime and violence. The relationship between methamphetamine use, anger and violence is complex and moderated by a range of individual, social and environmental factors. Treatment for methamphetamine use may be hindered by a propensity for anger in patients. This study utilises data from a randomised controlled trial of cognitive behaviour therapy for methamphetamine users to: (1) assess the reliability and validity of a measure of anger (the STAXI-2) in an Australian clinical sample of methamphetamine users; and (2) test the hypothesis that trait anger is prognostic of methamphetamine treatment outcome. A high level of internal consistency and factor analysis established the reliability and validity of the scale in this population group. A series of multivariate statistical models was developed to test whether trait anger upon entry to treatment is prognostic of treatment outcome. Contrary to the hypothesis, patients high in trait anger at baseline did no worse in treatment than patients with low trait anger; that is, trait anger did not modify the effect of treatment. These findings show that the STAXI-2 is a valid measure of anger in this population group and that high levels of trait anger should not be considered a barrier to the delivery of effective treatment to patients with methamphetamine use disorders.