Poster 273USE OF HIGH POTENCY CANNABIS IS PARTICULARLY ASSOCIATEDWITH ONSET OF PSYCHOSIS

Craig Morgan, Simona A. Stilo, Alessandra Papparelli, AuroraFalcone, Sonija Luzi, Valeria Mondelli, Clare Flach,John Powell, Robin M MurrayInstitute of Psychiatry, London, London, United Kingdom

Background: Epidemiological studies have reported that the risk ofdeveloping psychosis in cannabis users is dose related. Experi-mental research has shown that the active constituent of cannabisresponsible for its psychotogenic effect is Delta-9-Tetrahydrocan-nabinol (THC). Recent evidence shows the potency (% TCH) of thecannabis seized in the UK is increasing. Previous studies have alsosuggested that age at first use of cannabis might moderate thedegree of risk for developing a psychotic disorder. We predictedthat first episode psychosis patients would be more likely to havestarted using cannabis in early adolescence, to use higher potencycannabis and to use it more frequently than controls.Methods: We collected information concerning socio-demographicand clinical characteristics, and cannabis use (age at first use,frequency, length of use, type of cannabis used) from 280 first-episode psychosis (FEP) patients and 174 matched healthyvolunteers in South London.Results: Therewasno significant difference in the life-timeprevalenceof cannabis use or age at first use between cases and controls.Nevertheless, in the cases group age at first use was positivelycorrelated with age of onset of psychosis: the earlier the age at firstcannabis use, the earlier the onset of psychosis (z=0.49; p<0.001).After adjusting for age, gender, ethnicity, level of education, employ-ment status other stimulants use, cases were more likely to be regularusers (OR=6.4; 95% CI 3.2-28.6) and to have smoked high potencycannabis (skunk), (OR=6.8; 95% CI 2.6-25.4) than controls. Given aprevalence of 44% for skunk use among our cases and an OR=2.6 forskunk use in cases versus controls, we calculated a populationattributable fraction (PAF) for skunk use=27%.Discussion: Patients with first episode psychosis have smokedhigher potency cannabis (skunk), for longer and with greaterfrequency, than healthy controls. Moreover, age at first cannabis usesignificantly moderates age of onset for psychosis. Our findings alsosuggest that if skunk use was abolished 27% of the psychosis casesin South East London would be prevented.

doi:10.1016/j.schres.2010.02.1038

Poster 274THE GENETIC ASSOCIATION BETWEEN CANCER ANDSCHIZOPHRENIA: AN EPIDEMIOLOGICAL APPROACH

Gilad Gal1, Itzhak Levav2, Raz Gross11The Gertner Institute for Epidemiology and Health Policy Research,Sheba Medical Center, Israel; 2Ministry of Health, Jeruaslem, Israel

Background: Several studies have found lower incidence of canceramong patients with schizophrenia compared to the generalpopulation. Considering the well documented inheritance inschizophrenia, the hypothesis that there is a protective geneticfactor (against cancer) in patients with schizophrenia is plausible. Ifthe reduced incidence of cancer among schizophrenia patients isrelated to a genetic factor, it is expected that reduced incidence willbe found also among their first degree relatives. Indeed, a recentepidemiological study conducted in Israel indicated a reduced risk

of several cancer cites among parents of schizophrenia patients. Wehave further studied the genetic hypothesis by comparing parentsof schizophrenia patients, studying the relationship betweenschizophrenia and cancer within our population. Cancer rates werecompared between parents of schizophrenia patients with a knownfamily history of schizophrenia ("high" genetic load) to that ofparents of patients with no such family history ("low" genetic load).We hypothesized that lower cancer rates will be found in parents ofpatients with a high genetic load compared to parents with lowgenetic load. This study adds important information to the genetichypothesis of the association between cancer and schizophrenia.Methods: The study was based on cross linkage between twonational data bases in Israel: the Psychiatric Registry and the CancerRegistry. The data includes 7,014 schizophrenia patients and 37,653of their FDR. A familial aggregation measure for schizophrenia wascalculated for each subject according to the Bayesian theorm, andserve as a genetic weight measure. The calculation accounted forthe number of members diagnosed with schizophrenia and thenumber of family members. Each sibship (proband and sibs) had anidentical weight value, while each parent had a weight valueindependent of the other parent’s weight. The relationship betweenschizophrenia and cancer was examined within our population. Thefirst analysis was conducted on parents’ data using logisticregression by the method of Generalized Estimating Equations(GEE), appropriate for correlated data arising from repeatedmeasurements. The outcome was cancer (yes/no) and the mainpredictor was the genetic measure in its continuous form. Separateanalyses were used to evaluate the association between schizo-phrenia and specific cancers according to an a priori hypotheses.Results: Contrary to the hypothesis a significant increased risk forany cancer site was observed among parents of schizophreniapatients. The adjusted analysis indicated an increase of 14% (95% CI1.03-1.26), and an increase of 23% for colon cancer (95% CI 1.01-1.52) for 10% increase in the genetic weight.Discussion: Significantly increased risk for cancer as a function ofthe genetic load of schizophrenia was observed among parents ofschizophrenia patients. Thus, the genetic load as defined by familialreoccurrence of schizophrenia was associated with an increasedrather then decreased risk for cancer site. These outcomes do notsupport the genetic hypothesis of the association between cancerand schizophrenia.

doi:10.1016/j.schres.2010.02.1039

POSTER SESSION 2 & LUNCHMonday, 12 April, 2010 12:00pm-1:30pm

Poster 1MEASURING AUTISTIC TRAITS IN PATIENTS WITH SCHIZOPHRENIA

Tove Lugnegård1, Maria Unenge Hallerbäck1, Christopher Gillberg21Central Hospital Karlstad, Värmland, Sweden; 2University ofGothenburg Göteborg, Västra Götaland, Sweden

Background: Schizophrenia and Asperger syndrome are opera-tionalised diagnoses that are separated clinically according to age ofonset, symptom profile and outcome. Still, the disorders have majordifficulties in common: neurocognitive deficits as well as deficits insocial cognition. Autism-Spectrum Quotient (AQ) is a widely usedinstrument for investigating autistic traits in different populations.However, it is not well known if a diagnosis of schizophreniainfluences the result on AQ. We wanted to examine autistic traits

Abstracts 299