The Clinical Impact of Substance Use in Schizophrenia: A Study in an Irish Population


  • Pádraig Casey School of Medicine, Trinity College, University of Dublin, Ireland
  • Aiden Corvin Department of Psychiatry, Trinity College, University of Dublin, Ireland




Background: Substance use may be a risk factor for the onset of schizophrenia. However to date the impact of substance use in schizophrenia has not been fully explored in an Irish population. In this study we examine the clinical impact of substance use in schizophrenia within an Irish population.
Methods: The study sample consisted of 159 participants with a diagnosis of schizophrenia who were recruited to the ongoing Resource for Psychoses Genomics Ireland Study. All participants were interviewed with the Structured Clinical Interview for Diagnostic Statistical Manual IV to confirm diagnosis. Information on age at onset, illness course and substance use was collected at this interview and from case note review.
Results: In total, 48% of the participants reported lifetime substance use (including alcohol misuse). Cannabis was the most commonly used substance (82% of all users). Cannabis had an independent effect on the age at onset of psychosis, after adjusting for gender and use of substances other than cannabis. There was a trend towards more positive psychotic symptoms in substance users but it was not statistically significant.
Conclusions: Our results confirm the high lifetime prevalence of substance use in schizophrenia. In addition, results show an earlier age at onset of illness in cannabis users. This provides further evidence for the association between cannabis use and onset of schizophrenia, although causality cannot be assumed.

Author Biography

Pádraig Casey, School of Medicine, Trinity College, University of Dublin, Ireland

Sixth Year Medicine


1.Blanchard JJ, Brown SA, Horan WP, Sherwood AR. Substance use disorders in schizophrenia: review, integration and a proposed model. Clin. Psychol. Rev. 2000 Mar;20(2):207-34
2.Kavanagh DJ, Waghorn G, Jenner L et al. Demographic and clinical correlates of comorbid substance use disorders in psychosis: multivariate analyses from an epidemiological sample. Schizophr. Res. 2004 Feb 1;66:115-24
3.Semple DM, McIntosh AM, Lawrie SM. Cannabis as a risk factor for psychosis: systematic review. J. Psychopharmacol. 2005 Mar;19:187-94
4. Talamo A, Centorrino F, Tondo L, Dimitri A, Hennen J, Baldessarini GJ. Co-mor- bid substance use in schizophrenia: relation to positive and negative symptoms. Schizophr. Res. 2006 Sept;86(1-3):251-5
5.Kalami M, Kelly L, Gerwin M, Browne S, Larkin C, O’ Callaghan E. The preva- lence of comorbid substance misuse and its influence on suicidal ideation among in-patients with schizophrenia. Acta. Psychiatr. Scand. 2000;101:452-6
6.Kay SR, Opler LA, Friszbie A. Positive and negative syndrome scale (PANSS) rating manual. New York: Department of Psychiatry, Albert Einstein College of Medicine, Monteforte Medical Centre and Schizophrenia Research Unit, 1986 7.American Psychiatric Association. The Diagnostic and Statistical Manual of Men- tal Disorders- IV. Axis V: The global assessment of functioning scale
8.Smit F, Bolier L, Cuijpers P. Cannabis use and the risk of later schizophrenia: a review. Addiction. 2004 Apr;99:425-30
9.Addington J, Addington D. Effect of substance misuse in early psychosis. Br. J. Psychiatry Suppl. 1998;172 (suppl 33):134-6
10.Hambrecht M, Hafner H. Cannabis, vulnerability and the onset of schizophre- nia: an epidemiological perspective. Aust. N. Z. J. Psychiatry. 2000 Jun;34:468-75 11.Barnes TR, Mutsatsa SH, Hutton SB, Watt HC, Joyce EM. Co-morbid sub- stance use and age at onset of schizophrenia. Br. J. Psychiatry. (2006) Mar;188:237-42
12.Dubertret C, Bidard I, Ades J, Gorwood P. Lifetime positive symptoms in partici- pants with schizophrenia and cannabis use are partially explained by co-morbid addiction. Schizophr. Res. 2006 Sep;86:284-90




How to Cite

Casey, P., & Corvin, A. (2008). The Clinical Impact of Substance Use in Schizophrenia: A Study in an Irish Population. Trinity Student Medical Journal, 9(1), Page 14–17. Retrieved from