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Schizophr Bull. 2019 Jul 29. pii: sbz077. doi: 10.1093/schbul/sbz077. [Epub ahead of print]

Premorbid Adjustment and IQ in Patients With First-Episode Psychosis: A Multisite Case-Control Study of Their Relationship With Cannabis Use.

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Department of Biomedicine, Neuroscience and Advanced Diagnostics (BiND), Psychiatry Section, University of Palermo, Palermo, Italy.
2Department of Psychosis Studies, Institute of Psychiatry, King's College London, London, UK.
Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
National Institute for Health Research (NIHR) Mental Health Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College London, London, UK.
South London and Maudsley NHS Mental Health Foundation Trust, London, UK.
Department of Health Promotion Sciences Maternal and Infant Care, Internal Medicine and Medical Specialities, University of Palermo, Palermo, Italy.
Department of Economic, Management and Statistical Sciences (DSEAS) University of Palermo, Palermo, Italy.
Department of Health Service and Population Research, Institute of Psychiatry, King's College London, London, UK.
Centre for Genomic Sciences, Li KaShing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Department of Psychiatry, Early Psychosis Section, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands.
Departments of Psychiatry and Preventive Medicine, Icahn School of Medicine at Mount Sinai, New York, NY.
Department of Psychiatry, University of Cambridge, Herchel Smith Building for Brain & Mind Sciences, Cambridge, UK.
Psylife Group, Division of Psychiatry, University College London, London, UK.
Department of Psychiatry and Neuropsychology, School for Mental Health and Neuroscience, South Limburg Mental Health Research and Teaching Network, Maastricht University Medical Centre, Maastricht, The Netherlands.
Division of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University, Cardiff, UK.
Department of Child and Adolescent Psychiatry, Hospital General Universitario Gregorio Marañón, School of Medicine, Universidad Complutense, IiSGM, CIBERSAM, Madrid, Spain.
Barcelona Clinic Schizophrenia Unit, Neuroscience Institute, Hospital Clinic of Barcelona, Department of Medicine, University of Barcelona, IDIBAPS, CIBERSAM, Barcelona, Spain.
Department of Medicine, Psychiatry Area, School of Medicine, Universidad de Oviedo, ISPA, INEUROPA, CIBERSAM, Oviedo, Spain.
Department of Psychiatry, School of Medicine, Universidad de Valencia, CIBERSAM, Valencia, Spain.
Department of Psychiatry, Servicio de Psiquiatría Hospital "Virgen de la Luz," Cuenca, Spain.
Department of Psychiatry, Psychiatric Genetic Group, Instituto de Investigación Sanitaria de Santiago de Compostela, Complejo Hospitalario Universitario de Santiago de Compostela, Santiago de Compostela, Spain.
Department of Medical and Surgical Sciences, Psychiatry Unit, Alma Mater Studiorum Università di Bologna, Bologna, Italy.
Etablissement Public de Santé Maison Blanche, Paris, France.
INSERM, Créteil, France.
Division of Psychiatry, Department of Neuroscience and Behaviour, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil.
Rivierduinen Institute for Mental Health Care, Leiden, The Netherlands.
Department of Addiction, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
CAMEO Early Intervention Service, Cambridgeshire & Peterborough NHS Foundation Trust, Cambridge, UK.
Brain Centre Rudolf Magnus, Utrecht University Medical Centre, Utrecht, The Netherlands.


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.


cognition; education; marijuana; preillness; schizophrenia; sociability


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