Premorbid Adjustment and IQ in Patients With First-Episode Psychosis: A Multisite Case-Control Study of Their Relationship With Cannabis Use
Authors: Ferraro Laura , La Cascia Caterina , Quattrone Diego , Sideli Lucia , Matranga Domenica , Capuccio Veronica , Tripoli Giada , Gayer-Anderson Charlotte , Morgan Craig , Sami Musa B , Sham Pak , de Haan Lieuwe , Velthorst Eva , Jongsma Hannah E , Kirkbride James B , Rutten Bart P F , Richards Alexander L , Roldan Laura , Arango Celso , Bernardo Miquel , Bobes Julio , Sanjuan Julio , Santos Jose Luis , Arrojo Manuel , Tarricone Ilaria , Tortelli Andrea , Szöke Andrei , Del-Ben Cristina Marta , Selten Jean-Paul , Lynskey Michael , Jones Peter B , Van Os Jim , La Barbera Daniele ,   WP2 EU-GEI GROUP, Murray Robin M , Di Forti Marta , Amoretti Silvia , Baudin Grégoire , Beards Stephanie , Berardi Domenico , Bonetto Chiara , Cabrera Bibiana , Carracedo Angel , Charpeaud Thomas , Costas Javier , Cristofalo Doriana , Cuadrado Pedro , Ferchiou Aziz , Franke Nathalie , Frijda Flora , García Bernardo Enrique , Garcia-Portilla Paz , González Peñas Javier , González Emiliano , Hubbard Kathryn , Jamain Stéphane , Jiménez-López Estela , Lasalvia Antonio , Leboyer Marion , López Montoya Gonzalo , Lorente-Rovira Esther , M Díaz-Caneja Covadonga , Marcelino Loureiro Camila , Marrazzo Giovanna , Martínez Covadonga , Matteis Mario , Messchaart Elles , Moltó Ma Dolores , Moreno Carmen , Juan Nacher , Olmeda Ma Soledad , Parellada Mara , Pignon Baptiste , Rapado Marta , Richard Jean-Romain , Rodríguez Solano José Juan , Rossi Menezes Paulo , Ruggeri Mirella , Sáiz Pilar A , Sánchez-Gutierrez Teresa , Sánchez Emilio , Sartorio Crocettarachele , Schürhoff Franck , Seminerio Fabio , Shuhama Rosana , Stilo Simona A , Termorshuizen Fabian , Tosato Sarah , Tronche Anne-Marie , van Dam Daniella , van der Ven Elsje 
Published: July 2019

Abstract
Psychotic patients with a lifetime history of cannabis use generally show better cognitive functioning than other psychotic patients. Some authors suggest that cannabis-using patients may have been less cognitively impaired and less socially withdrawn in their premorbid life. Using a dataset comprising 948 patients with first-episode psychosis (FEP) and 1313 population controls across 6 countries, we examined the extent to which IQ and both early academic (Academic Factor [AF]) and social adjustment (Social Factor [SF]) are related to the lifetime frequency of cannabis use in both patients and controls. We expected a higher IQ and a better premorbid social adjustment in psychotic patients who had ever used cannabis compared to patients without any history of use. We did not expect such differences in controls. In both patients and controls, IQ was 3 points higher among occasional-users than in never-users (mean difference [Mdiff] = 2.9, 95% CI = [1.2, 4.7]). Both cases and control daily-users had lower AF compared to occasional (Mdiff = −0.3, 95% CI = [−0.5; −0.2]) and never-users (Mdiff = −0.4, 95% CI = [−0.6; −0.2]). Finally, patient occasional (Mdiff = 0.3, 95% CI = [0.1; 0.5]) and daily-users (Mdiff = 0.4, 95% CI = [0.2; 0.6]) had better SF than their never-using counterparts. This difference was not present in controls (Fgroup*frequency(2, 2205) = 4.995, P = .007). Our findings suggest that the better premorbid social functioning of FEP with a history of cannabis use may have contributed to their likelihood to begin using cannabis, exposing them to its reported risk-increasing effects for Psychotic Disorders.