Skip to main content
    • Aa
    • Aa

Cannabis use and childhood trauma interact additively to increase the risk of psychotic symptoms in adolescence

  • M. Harley (a1) (a2), I. Kelleher (a1), M. Clarke (a1), F. Lynch (a2), L. Arseneault (a3), D. Connor (a1), C. Fitzpatrick (a2) and M. Cannon (a1)...

Adolescent cannabis use has been shown in many studies to increase the risk of later psychosis. Childhood trauma is associated with both substance misuse and risk for psychosis. In this study our aim was to investigate whether there is a significant interaction between cannabis use and childhood trauma in increasing the risk for experiencing psychotic symptoms during adolescence.


Psychiatric interviews using the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS) semi-structured instrument were carried out with 211 adolescents aged between 12 and 15 years and their parents as part of a population-based study. The interview enquired about early traumatic events, cannabis use and psychiatric symptoms in adolescence.


In separate analyses both cannabis use and childhood trauma were significantly associated with risk of experiencing psychotic symptoms. However, the presence of both childhood trauma and early cannabis use significantly increased the risk for psychotic symptoms beyond the risk posed by either risk factor alone, indicating that there was a greater than additive interaction between childhood trauma and cannabis use.


Our finding of a greater than additive interaction between childhood trauma and cannabis use may have implications for the identification of individuals at high risk of experiencing psychotic symptoms. For example, measures to actively discourage or intensively treat cannabis use in children and adolescents who have experienced abuse may help to prevent the development of psychosis in this vulnerable group. Our findings require replication in larger samples to confirm this interaction effect.

Corresponding author
*Address for correspondence: Professor M. Cannon, Department of Psychiatry, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin 9, Ireland. (Email:
Linked references
Hide All

This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

M Cannon , M Harley , MC Clarke , L Arseneault (2006). Genes, cannabis and psychosis. In Beyond Nature and Nurture in Psychiatry: Genes, Environment and their Interplay (ed. J. MacCabe , O. O'Daly , R. M. Murray , P. McGuffin and P. Wright ), ch. 16, pp. 141155. Informa UK Ltd: Abingdon, Oxon.

CD Verrico , JD Jentsch , RH Roth (2003). Persistent and anatomically selective reduction in prefrontal cortical dopamine metabolism after repeated intermittent cannabinoid administration in rats. Synapse 49, 6166.

Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Psychological Medicine
  • ISSN: 0033-2917
  • EISSN: 1469-8978
  • URL: /core/journals/psychological-medicine
Please enter your name
Please enter a valid email address
Who would you like to send this to? *



Altmetric attention score

Full text views

Total number of HTML views: 8
Total number of PDF views: 123 *
Loading metrics...

Abstract views

Total abstract views: 546 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 20th September 2017. This data will be updated every 24 hours.