![Sample our Health and Social Care journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/5938/TOC-Subject-Sample-2021-Health-Social-Care.jpg"})
Abstract
Aims: To examine the effect of frequent cannabis use at various times during the lifetime upon the development of psychotic symptoms and of schizophrenia.
Design: Cannabis use was examined within the Edinburgh High Risk Study (EHRS), a prospective study of young people at enhanced genetic risk for schizophrenia.
Participants: High risk and control subjects of the EHRS.
Measurements: Childhood Behaviour Checklist; sub‐scales of the Present State Examination; self report of substances use, particularly of cannabis.
Findings: Within the group at high genetic risk, there was a strong association between illness onset and frequent cannabis use just prior to onset. Cannabis use at earlier times showed no such association. The effect, however, was considerably weakened once various childhood behaviours, particularly social withdrawal and aggressiveness, were taken into account. Those who fell ill with schizophrenia and who used cannabis frequently showed higher levels of some symptoms than those who fell ill and did not use cannabis frequently.
Conclusions: Social problems and aggressiveness aged between 13 and 16 mostly account for both cannabis use and illness onset. Heavy use is, however, associated with high levels of symptoms and may act as a trigger carrying a vulnerable person over a threshold into psychotic illness.
Acknowledgements
This study was carried out with the approval of the Ethical Committees of the relevant areas. It was supported financially by two programme grants from the Medical Research Council. The sustained co‐operation of the families involved is acknowledged with gratitude. We also thank Norma Brearley for the careful preparation of the manuscript. There is no conflict of interest involved.