Wednesday, March 2, 2011

Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study



The abstract of an article published in the March 1st edition of the British Medical Journal:

By Rebecca Kuepper, research psychologist (1), Jim van Os, professor (1), visiting professor (2), Roselind Lieb, professor (3,4), Hans-Ulrich Wittchen, professor (4,5), Michael Höfler, research statistician (5), Cécile Henquet, lecturer (1)
  1. Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University Medical Center, Maastricht, Netherlands
  2. King’s College London, King’s Health Partners, Department of Psychosis Studies, Institute of Psychiatry, London, UK
  3. Department of Psychology, Division of Epidemiology and Health Psychology, University of Basel, Switzerland
  4. Max Planck Institute of Psychiatry, Munich, Germany
  5. Institute of Clinical Psychology and Psychotherapy, Technical University Dresden, Germany

Objective

To determine whether use of cannabis in adolescence increases the risk for psychotic outcomes by affecting the incidence and persistence of subclinical expression of psychosis in the general population (that is, expression of psychosis below the level required for a clinical diagnosis).


Design

Analysis of data from a prospective population based cohort study in Germany (early developmental stages of psychopathology study).


Setting

Population based cohort study in Germany.


Participants

1923 individuals from the general population, aged 14-24 at baseline.


Main outcome measure

Incidence and persistence of subthreshold psychotic symptoms after use of cannabis in adolescence. Cannabis use and psychotic symptoms were assessed at three time points (baseline, T2 (3.5 years), T3 (8.4 years)) over a 10 year follow-up period with the Munich version of the composite international diagnostic interview (M-CIDI).


Results

In individuals who had no reported lifetime psychotic symptoms and no reported lifetime cannabis use at baseline, incident cannabis use over the period from baseline to T2 increased the risk of later incident psychotic symptoms over the period from T2 to T3 (adjusted odds ratio 1.9, 95% confidence interval 1.1 to 3.1; P=0.021). Furthermore, continued use of cannabis increased the risk of persistent psychotic symptoms over the period from T2 to T3 (2.2, 1.2 to 4.2; P=0.016). The incidence rate of psychotic symptoms over the period from baseline to T2 was 31% (152) in exposed individuals versus 20% (284) in non-exposed individuals; over the period from T2 to T3 these rates were 14% (108) and 8% (49), respectively.


Conclusion

Cannabis use is a risk factor for the development of incident psychotic symptoms. Continued cannabis use might increase the risk for psychotic disorder by impacting on the persistence of symptoms.

Posting of this abstract is for the purposes of research into psychosis.

Also see:

Cannabis use 'raises psychosis risk' - study

Cannabis use 'doubles risk of psychosis for teenagers'

Marijuana Use Linked to Risk of Psychotic Symptoms

Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study


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