Corinne Prescott

Economic impact of early intervention in people at high risk of psychosis

Background Despite the increasing development of early intervention services for psychosis, little is known about their cost-effectiveness. We assessed the cost-effectiveness of Outreach and Support in South London (OASIS), a service for people with an at-risk mental state (ARMS) for psychosis. Method The costs of OASIS compared to care as usual (CAU) were entered in a decision model and examined for 12- and 24-month periods, using the duration of untreated psychosis (DUP) and rate of transition to psychosis as key parameters. The costs were calculated on the basis of services used following referral and the impact on employment. Sensitivity analysis was used to test the robustness of all the assumptions made in the model. Results Over the initial 12 months from presentation, the costs of the OASIS intervention were £1872 higher than CAU. However, after 24 months they were £961 less than CAU. Conclusions This model suggests that services that permit early detection of people at high risk of psychosis may be cost saving.

Virtual reality and paranoid ideations in people with an ‘at-risk mental state’ for psychosis

BACKGROUND Virtual reality provides a means of studying paranoid thinking in controlled laboratory conditions. However, this method has not been used with a clinical group. AIMS To establish the feasibility and safety of using virtual reality methodology in people with an at-risk mental state and to investigate the applicability of a cognitive model of paranoia to this group. METHOD Twenty-one participants with an at-risk mental state were assessed before and after entering a virtual reality environment depicting the inside of an underground train. RESULTS Virtual reality did not raise levels of distress at the time of testing or cause adverse experiences over the subsequent week. Individuals attributed mental states to virtual reality characters including hostile intent. Persecutory ideation in virtual reality was predicted by higher levels of trait paranoia, anxiety, stress, immersion in virtual reality, perseveration and interpersonal sensitivity. CONCLUSIONS Virtual reality is an acceptable experimental technique for use with individuals with at-risk mental states. Paranoia in virtual reality was understandable in terms of the cognitive model of persecutory delusions.

S06-04 Skunk and psychosis in South East London

Background Epidemiological studies have reported that the increased risk of developing psychosis in cannabis users is dose related. In addition, experimental research has shown that the active constituent of cannabis responsible for its psychotogenic effect is Delta-9-Tetrahydrocannabinol (THC) (Murray et al, 2007). Recent evidence has suggested an increased in potency (% TCH) in the cannabis seized in the UK (Potter et al, 2007). Hypothesis We predicted that first episode psychosis patients are more likely to use higher potency cannabis and more frequently than controls. Methods We collected information concerning socio-demographic, clinical characteristics and cannabis use (age at first use, frequency, length of use, type of cannabis used) from a sample of 191 first-episode psychosis patients and 120 matched healthy volunteers. All were recruited as part of the Genetic and Psychosis (GAP) study which studied all patients who presented to the South London and Maudsley Trust. Results There was no significant difference in the life-time prevalence of cannabis use or age at first use between cases and controls. However, cases were more likely to be regular users (p=0.05), to be current users (p=0.04) and to have smoked cannabis for longer (p=0.01). Among cannabis users, 86.8% of 1st Episode Psychosis Patients preferentially used Skunk/Sinsemilla compared to 27.7% of Controls. Only 13.2 % of 1st Episode psychosis Patients chose to use Resin/Hash compared to 76.3% of controls. The concentration of TCH in these in South East London, ranges between 8.5 and 14 % (Potter et al, 2007). Controls (47%) were more likely to use Hash (Resin) whose average TCH concentration is 3.4% (Potter et al, 2007). Conclusions Patients with first episode psychosis have smoked higher potency cannabis, for longer and with greater frequency, than healthy controls.