Part one is a meta-analytic review comparing the efficacy of virtual reality treatments (VRTs) and standard psychological therapies for achieving mental health symptom reduction. Outcomes from twenty-two randomised-controlled trials were quality assessed and meta-analysed. Results indicated that VRTs were equal to, and in some cases superior to comparative treatments, depending on the type of mental health problem being treated. Methodological and heterogeneity issues complicate interpretation. Continued methodologically robust research is required before recommendations for practice can be made with confidence. Part two presents an empirical study in which virtual reality (VR) was used to investigate emotional reactivity and aggression in antisocial personality disorder (ASPD). Fifteen individuals diagnosed with ASPD and twenty healthy volunteers took part in VR provocation. In response, ASPD participants showed greater negative emotional reactivity, less prosocial behaviour, and a trend towards more aggression than healthy volunteers. Findings tentatively support the notion that ASPD entails difficulties regulating emotions and inhibiting aggression under conditions of perceived threat. Modified large-scale replications are required to substantiate findings. Improved understanding could inform practices for assessing and treating risk of aggression/violence in this population. Part three is a critical appraisal of the empirical study. It describes my background interest in the research area and critiques a multi-method approach to measurement. The potential for VR to be used as a tool to assess and treat criminogenic risk in ASPD is discussed in more detail. It concludes with personal reflections, highlighting some of the ethical and risk management considerations raised by conducting research with this population.