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Meta-Analysis
. 2014 Oct 14;2014(10):CD004837.
doi: 10.1002/14651858.CD004837.pub3.

Cannabis and schizophrenia

Benjamin C McLoughlin  1 , Jonathan A Pushpa-Rajah, Donna Gillies, John Rathbone, Hannele Variend, Eliana Kalakouti, Katerina Kyprianou
Affiliations
Meta-Analysis

Cannabis and schizophrenia

Benjamin C McLoughlin et al. Cochrane Database Syst Rev. .

Abstract

Background: Schizophrenia is a mental illness causing disordered beliefs, ideas and sensations. Many people with schizophrenia smoke cannabis, and it is unclear why a large proportion do so and if the effects are harmful or beneficial. It is also unclear what the best method is to allow people with schizophrenia to alter their cannabis intake.

Objectives: To assess the effects of specific psychological treatments for cannabis reduction in people with schizophrenia.To assess the effects of antipsychotics for cannabis reduction in people with schizophrenia.To assess the effects of cannabinoids (cannabis related chemical compounds derived from cannabis or manufactured) for symptom reduction in people with schizophrenia.

Search methods: We searched the Cochrane Schizophrenia Group Trials Register, 12 August 2013, which is based on regular searches of BIOSIS, CINAHL, EMBASE, MEDLINE, PUBMED and PsycINFO.We searched all references of articles selected for inclusion for further relevant trials. We contacted the first author of included studies for unpublished trials or data.

Selection criteria: We included all randomised controlled trials involving cannabinoids and schizophrenia/schizophrenia-like illnesses, which assessed:1) treatments to reduce cannabis use in people with schizophrenia;2) the effects of cannabinoids on people with schizophrenia.

Data collection and analysis: We independently inspected citations, selected papers and then re-inspected the studies if there were discrepancies, and extracted data. For dichotomous data we calculated risk ratios (RR) and for continuous data, we calculated mean differences (MD), both with 95% confidence intervals (CI) on an intention-to-treat basis, based on a fixed-effect model. We excluded data if loss to follow-up was greater than 50%. We assessed risk of bias for included studies and used GRADE to rate the quality of the evidence.

Main results: We identified eight randomised trials, involving 530 participants, which met our selection criteria.For the cannabis reduction studies no one treatment showed superiority for reduction in cannabis use. Overall, data were poorly reported for many outcomes of interest. Our main outcomes of interest were medium-term data for cannabis use, global state, mental state, global functioning, adverse events, leaving the study early and satisfaction with treatment. 1. Reduction in cannabis use: adjunct psychological therapies (specifically about cannabis and psychosis) versus treatment as usualResults from one small study showed people receiving adjunct psychological therapies specifically about cannabis and psychosis were no more likely to reduce their intake than those receiving treatment as usual (n = 54, 1 RCT, MD -0.10, 95% CI -2.44 to 2.24, moderate quality evidence). Results for other main outcomes at medium term were also equivocal. No difference in mental state measured on the PANSS positive were observed between groups (n = 62, 1 RCT, MD -0.30 95% CI -2.55 to 1.95, moderate quality evidence). Nor for the outcome of general functioning measured using the World Health Organization Quality of Life BREF (n = 49, 1 RCT, MD 0.90 95% CI -1.15 to 2.95, moderate quality evidence). No data were reported for the other main outcomes of interest 2. Reduction in cannabis use: adjunct psychological therapy (specifically about cannabis and psychosis) versus adjunct non-specific psychoeducation One study compared specific psychological therapy aimed at cannabis reduction with general psychological therapy. At three-month follow-up, the use of cannabis in the previous four weeks was similar between treatment groups (n = 47, 1 RCT, RR 1.04 95% CI 0.62 to 1.74, moderate quality evidence). Again, at a medium-term follow-up, the average mental state scores from the Brief Pscychiatric Rating Scale-Expanded were similar between groups (n = 47, 1 RCT, MD 3.60 95% CI - 5.61 to 12.81, moderate quality evidence). No data were reported for the other main outcomes of interest: global state, general functioning, adverse events, leaving the study early and satisfaction with treatment. 3. Reduction in cannabis use: antipsychotic versus antipsychotic In a small trial comparing effectiveness of olanzapine versus risperidone for cannabis reduction, there was no difference between groups at medium-term follow-up (n = 16, 1 RCT, RR 1.80 95% CI 0.52 to 6.22, moderate quality evidence). The number of participants leaving the study early at medium term was also similar (n = 28, 1 RCT, RR 0.50 95% CI 0.19 to 1.29, moderate quality evidence). Mental state data were reported, however they were reported within the short term and no difference was observed. No data were reported for global state, general functioning, and satisfaction with treatment.With regards to adverse effects data, no study reported medium-term data. Short-term data were presented but overall, no real differences between treatment groups were observed for adverse effects. 4. Cannabinoid as treatment: cannabidiol versus amisulprideAgain, no data were reported for any of the main outcomes of interest at medium term. There were short-term data reported for mental state using the BPRS and PANSS, no overall differences in mental state were observed between treatment groups.

Authors' conclusions: Results are limited and inconclusive due to the small number and size of randomised controlled trials available and quality of data reporting within these trials. More research is needed to a) explore the effects of adjunct psychological therapy that is specifically about cannabis and psychosis as currently there is no evidence for any novel intervention being better than standard treatment,for those that use cannabis and have schizophrenia b) decide the most effective drug treatment in treating those that use cannabis and have schizophrenia, and c) assess the effectiveness of cannabidiol in treating schizophrenia. Currently evidence is insufficient to show cannabidiol has an antipsychotic effect.

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Conflict of interest statement

None known.

Figures

1
1
Cannabis sativa
2
2
delta‐9‐tetrahydrocannabinol (THC)
3
3
Study flow diagram: 2013 search.
4
4
5
5
1.1
1.1. Analysis
Comparison 1 CANNABIS REDUCTION: ADJUNCT PSYCHOLOGICAL THERAPY versus TREATMENT AS USUAL, Outcome 1 Behaviour: Cannabis use: 1. Frequency of use (ASI, group‐based therapy, high = bad).
1.6
1.6. Analysis
Comparison 1 CANNABIS REDUCTION: ADJUNCT PSYCHOLOGICAL THERAPY versus TREATMENT AS USUAL, Outcome 6 Mental state: 2. Average insight score (Birchwood Insight Scale, high score = better).
1.7
1.7. Analysis
Comparison 1 CANNABIS REDUCTION: ADJUNCT PSYCHOLOGICAL THERAPY versus TREATMENT AS USUAL, Outcome 7 Mental state: 3. Average negative symptom score (PANSS, high score = poor).
1.10
1.10. Analysis
Comparison 1 CANNABIS REDUCTION: ADJUNCT PSYCHOLOGICAL THERAPY versus TREATMENT AS USUAL, Outcome 10 Mental state: 4c. Average positive symptom score (PANSS, high score = poor).
1.11
1.11. Analysis
Comparison 1 CANNABIS REDUCTION: ADJUNCT PSYCHOLOGICAL THERAPY versus TREATMENT AS USUAL, Outcome 11 General functioning: 1. Subjective quality of life (WHO QOL, brief, high score = better).
1.12
1.12. Analysis
Comparison 1 CANNABIS REDUCTION: ADJUNCT PSYCHOLOGICAL THERAPY versus TREATMENT AS USUAL, Outcome 12 General functioning: 3. Global functioning (GAF, high score = better).
1.14
1.14. Analysis
Comparison 1 CANNABIS REDUCTION: ADJUNCT PSYCHOLOGICAL THERAPY versus TREATMENT AS USUAL, Outcome 14 General functioning: 4. Global functioning (SOFAS, high score = better).
2.1
2.1. Analysis
Comparison 2 CANNABIS REDUCTION: PSYCHOLOGICAL THERAPY (SPECIFICALLY ABOUT CANNABIS AND PSYCHOSIS) versus NON‐SPECIFIC PSYCHOEDUCATION, Outcome 1 Behaviour: Cannabis use: 1. Used cannabis in last 4 weeks.
2.3
2.3. Analysis
Comparison 2 CANNABIS REDUCTION: PSYCHOLOGICAL THERAPY (SPECIFICALLY ABOUT CANNABIS AND PSYCHOSIS) versus NON‐SPECIFIC PSYCHOEDUCATION, Outcome 3 Mental state: 1. Average overall score (BPRS‐E total endpoint, high score = poor).
2.7
2.7. Analysis
Comparison 2 CANNABIS REDUCTION: PSYCHOLOGICAL THERAPY (SPECIFICALLY ABOUT CANNABIS AND PSYCHOSIS) versus NON‐SPECIFIC PSYCHOEDUCATION, Outcome 7 Global state: Average overall score (KAPQ total endpoint, high score = good).
2.8
2.8. Analysis
Comparison 2 CANNABIS REDUCTION: PSYCHOLOGICAL THERAPY (SPECIFICALLY ABOUT CANNABIS AND PSYCHOSIS) versus NON‐SPECIFIC PSYCHOEDUCATION, Outcome 8 General functioning: Average score (SOFAS total endpoint, high score = good).
3.1
3.1. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 1 Behaviour: Cannabis use: 1. Traces of cannabis breakdown products in urine (number of patients positive above threshold level ‐ 100 nanograms ‐ olanzapine versus risperidone).
3.4
3.4. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 4 Mental state: Average score (OCDUS, short term, high = poor) ‐ olanzapine versus risperdione.
3.5
3.5. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 5 Adverse effects: 1. Anticholinergic ‐ various (clozapine vs other antipsychotic).
3.6
3.6. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 6 Adverse effects: 2. Cardiac ‐ various (clozapine vs other antipsychotic).
3.7
3.7. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 7 Adverse effects: 3. Central nervous system / higher functions ‐ various (clozapine vs other antipsychotic).
3.8
3.8. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 8 Adverse effects: 4. Gastrointestinal ‐ various (clozapine vs other antipsychotic).
3.9
3.9. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 9 Adverse effects: 5. Metabolic ‐ weight gain (clozapine vs other antipsychotic).
3.10
3.10. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 10 Adverse effects: 6a. Movement disorders ‐ various (clozapine vs other antipsychotic).
3.11
3.11. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 11 Adverse events: 6b. Movement disorders ‐ average score (Simpson scale, high score = poor ‐ olanzapine versus risperidone).
3.12
3.12. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 12 Adverse effects: 7. Others ‐ various (clozapine vs other antipsychotic).
3.13
3.13. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 13 Leaving the study early: 1. Number leaving (olanzapine vs risperidone).
3.14
3.14. Analysis
Comparison 3 CANNABIS REDUCTION: ANTIPSYCHOTIC 'A' versus ANTIPSYCHOTIC 'B', Outcome 14 Leaving the study early: 2. Weeks in treatment (olanzapine vs risperidone).
4.1
4.1. Analysis
Comparison 4 CANNABINOID AS TREATMENT: CANNABIDIOL versus AMISULPRIDE, Outcome 1 Mental state: 1a. Average overall score (BPRS, total endpoint, high score = poor).
4.2
4.2. Analysis
Comparison 4 CANNABINOID AS TREATMENT: CANNABIDIOL versus AMISULPRIDE, Outcome 2 Mental state: 1b. Average overall score (PANSS, total endpoint, high score = poor).
4.3
4.3. Analysis
Comparison 4 CANNABINOID AS TREATMENT: CANNABIDIOL versus AMISULPRIDE, Outcome 3 Mental state: 2. Average negative symptom score (PANSS, high score = poor).
4.4
4.4. Analysis
Comparison 4 CANNABINOID AS TREATMENT: CANNABIDIOL versus AMISULPRIDE, Outcome 4 Mental state: 3. Average positive symptom score (PANSS, high score = poor).
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References

References to studies included in this review

Akerele 2007 {published data only (unpublished sought but not used)}
    1. Akerele E, Levin FR. Comparison of olanzapine to risperidone in substance‐abusing individuals with schizophrenia. American Journal on Addictions 2007;16(4):260‐8. [MEDLINE: ] - PubMed
Bonsack 2011 {published and unpublished data}
    1. Bonsack C, Gibellini Manetti S, Favrod J, Montagrin Y, Besson J, Bovet P, et al. Motivational intervention to reduce cannabis use in young people with psychosis: randomised control trial. Psychotherapy and Psychosomatics 2011;80(5):287‐97. - PubMed
Brunette 2011 {published data only (unpublished sought but not used)}
    1. Brunette MF, Dawson R, O’Keefe CD, Narasimhan M, Noordsy DL, Wojcik NJ, et al. A randomized trial of clozapine versus other antipsychotics for cannabis use disorder in patients with schizophrenia. Journal of Dual Diagnosis 2011;7(1‐2):50‐63. - PMC - PubMed
Edwards 2006 {published data only (unpublished sought but not used)}
    1. Edwards J. Early psychosis service developments: becoming real. 3rd International Conference on Early Psychosis; 2002 Sep 25‐28; Copenhagen, Denmark. 2002:56. [KA03]
    1. Edwards J, Elkins K, Hinton M, Harrigan SM, Donovan K, Athanasopoulos O, et al. Randomized controlled trial of a cannabis‐focused intervention for young people with first‐episode psychosis. Acta Psychiatrica Scandinavica 2006;114(2):109‐17. [MEDLINE: ] - PubMed
    1. Edwards J, Elkins KS, Hinton MF, Harrigan SM, Donovan KD, Athanasopoulos O. Randomized controlled trial of a cannabis‐focused intervention versus psychoeducation for young people continuing to use cannabis in the 12 months following entry to treatment for first‐episode psychosis. Schizophrenia Research 2004;70(1):61. [ISI:000224551100164]
Hjorthoj 2013 {published data only (unpublished sought but not used)}
    1. Hjorthj CR, Fohlmanna A, Larsena AM, Gluuda C, Arendta M, Nordentoft M. Specialized psychosocial treatment plus treatment as usual (TAU) versus TAU for patients with cannabis use disorder and psychosis: the CapOpus randomised trial. Psychological Medicine July 2013;43(7):1499‐510. - PubMed
Leweke 2012 {published data only (unpublished sought but not used)}
    1. Leweke FM, Piomelli D, Pahlisch F, Muhl D, Gerth CW, Hoyer C, et al. Cannabidiol enhances anandamide signalling and alleviates psychotic symptoms of schizophrenia. Translation Psychiatry 2012;2(94):1‐7. - PMC - PubMed
Madigan 2012 {published data only (unpublished sought but not used)}
    1. Madigan K, Brennan D, Lawlor E, Turner N, Kinsella A, O'Connor JJ, et al. A multi‐center, randomized control trial of a group psychological intervention for psychosis with comorbid cannabis dependence over the early course of the illness. Schizophrenia research 2013;143(1):138‐42. - PubMed
van Nimwegen 2008 {published data only (unpublished sought but not used)}
    1. Nimwegen L, Haan L, Beveren N, Laan W, Brink W, Linszen D. Subjective well‐being and craving for cannabis in first psychosis, a randomized double blind comparison of olanzapine vs risperidone. Canadian Jourmal of Psychiatry 2008;53(6):400–5. - PubMed

References to studies excluded from this review

Baker 2006 {published data only}
    1. Baker A, Bucci S, Lewin TJ, Kay‐Lambkin F, Constable PM, Carr VJ. Cognitive behavioural therapy for substance use disorders in people with psychotic disorders. British Journal of Psychiatry 2006;188:439‐48. - PubMed
Barrowclough 2010 {published data only}
    1. Barrowclough C, Haddock G, Wykes T, Beardmore R, Conrod P, Craig T, et al. Integrated motivational interviewing and cognitive behavioural therapy for people with psychosis and comorbid substance misuse: randomised controlled trial. BMJ 2010;341:c6325. - PMC - PubMed
Bellack 2006 {published data only}
    1. Bellack AS, Bennett ME, Gearon JS, Brown CH, Yang Y. A randomized clinical trial of a new behavioural treatment for drug abuse in people with severe and persistent mental illness. Archives of General Psychiatry 2006;63(4):426‐32. - PubMed
James 2004 {published data only}
    1. James W, Preston NJ, Koh G, Spencer C, Kisely SR, Castle DJ. A group intervention which assists patients with dual diagnosis reduce their drug use: a randomised control trial. Psychological Medicine 2004;34(6):983‐90. - PubMed
Kemp 2007 {published data only}
    1. Kemp R, Harris A, Vurel E, Sitharthan T. Stop using stuff: trial of a drug and alcohol intervention for young people with comorbid mental illness and drug and alcohol problems.. Australasian psychiatry 2007;15(6):490‐3. - PubMed
Martino 2006 {published data only}
    1. Matrino S, Carroll KM, Nich C, Rounsaville BJ. A randomised controlled pilot study of motivational interviewing for patients with psychotic and drug use disorders. Addiction 2006;101(10):1479‐92. - PubMed

References to studies awaiting assessment

D'Souza 2005 {published data only}
    1. D'Souza DC, Abi‐Saab WM, Madonick S, Forselius‐Bielen K, Doersch A, Braley G, et al. Delta‐9‐tetrahydrocannabinol effects in schizophrenia: implications for cognition, psychosis, and addiction. Biological Psychiatry 2005;57(6):594‐608. - PubMed

Additional references

Addington 1993
    1. Addington D, Addington J, Maticka‐Tyndale E. Assessing depression in schizophrenia: The Calgary Depression Scale. British Journal of Psychiatry 1993;163(22):39‐44. - PubMed
Allebeck 1993
    1. Allebeck P, Adamsson C, Engström A. Cannabis and schizophrenia: a longitudinal study of cases treated in Stockholm County. Acta Psychiatrica Scandinavica 1993;88(1):21‐4. - PubMed
Altman 1996
    1. Altman DG, Bland JM. Detecting skewness from summary information. BMJ 1996;313:1200. - PMC - PubMed
Andreasen 1983
    1. Andreasen NC. Negative symptoms in schizophrenia. Archives of General Psychiatry 1983;39:784‐8. - PubMed
Andreasen 1984
    1. Andreasen NC. The Scale for the Assessment of Positive Symptoms(SAPS). University of Iowa. Iowa City, Iowa 1984.
Andreasson 1987
    1. Andreasson S, Allebeck P, Engstrom A, Rydberg U. Cannabis and schizophrenia: a longitudinal study of Swedish conscripts. Lancet 1987;2:1483‐6. - PubMed
Arseneault 2002
    1. Arseneault L, Cannon M, Poulton R, Murray R, Caspi A, Moffit TE. Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study. BMJ 2002;325:1212‐3. - PMC - PubMed
Ashton 2001
    1. Ashton CH. Pharmacology and effects of cannabis: a brief review. British Journal of Psychiatry 2001;178:101‐6. - PubMed
Baigent 1995
    1. Baigent M, Holme G, Hafner RJ. Self reports of the interaction between substance abuse and schizophrenia. Australian and New Zealand Journal of Psychiatry 1995;29(1):69‐74. - PubMed
Beck 1972
    1. Beck AT, Beck RW. Screening depressed patients in family practice. A rapid technique. Postgraduate Medicine 1972;52:81‐5. - PubMed
Berridge 2004
    1. Berridge V. Cannabis Britannica: Empire, trade and prohibition. English Historical Review 2004;483:1075‐175.
Bersani 2002
    1. Bersani G, Orlandi V, Kotzalidis GD, Pancheri P. Cannabis and schizophrenia: impact on onset, course, psychopathology and outcomes. European Archives of Psychiatry and Clinical Neuroscience 2002;252(2):86‐92. - PubMed
Birchwood 1992
    1. Birchwood M, Smith J, Cochrane R. Specific and non‐specific effects of educational intervention for families living with schizophrenia. A comparison of three methods. British Journal of Psychiatry 1992;160:806‐14. - PubMed
Birchwood 1993
    1. Birchwood M, Smith J, Drury V, Healy J, Macmillan F, Slade M. A self‐report Insight scale for psychosis: reliability, validity and sensitivity to change. Acta Psychiatrica Scandinavica Jan 1994;89(1):62‐7. - PubMed
Bland 1997
    1. Bland JM, Kerry SM. Statistics notes. Trials randomised in clusters. BMJ 1997;315:600. - PMC - PubMed
Bodlund 1994
    1. Bodlund O, Kullgren G, Ekselius L. Axis V—Global Assessment of Functioning Scale. Evaluation of a self‐report version. Acta Psychiatrica Scandinavica November 1994;90(5):342‐7. - PubMed
Boissel 1999
    1. Boissel JP, Cucherat M, Li W, Chatellier G, Gueyffier F, Buyse M, et al. The problem of therapeutic efficacy indices. 3. Comparison of the indices and their use. Therapie 1999;54(4):405‐11. - PubMed
Carney 1984
    1. Carney M, Bacelle L, Robinson B. Psychosis after cannabis use. BMJ 1984;288:1047. - PMC - PubMed
Carpenter 1994
    1. Carpenter WT Jr, Buchanan RW. Schizophrenia. New England Journal of Medicine 1994;330:681‐90. - PubMed
Casadio 2011
    1. Casadioa P, Fernandes C, Murray RM, Forti M. Cannabis use in young people: the risk for schizophrenia. Neuroscience and biobehavioral reviews 2011;35(8):1779‐87. - PubMed
Chopra 1974
    1. Chopra GS, Smith JW. Psychotic reactions following cannabis use in East Indians. Archives of General Psychiatry 1974;30:24‐7. - PubMed
Condren 2001
    1. Condren RM, O’Connor J, Browne R. Prevalence and patterns of substance misuse in schizophrenia. A catchment area case‐control study. Psychiatric Bulletin 2001;25(1):17‐20.
D'Souza 2009
    1. D'Souza DC, Sewell RA, Ranganathan M. Cannabis and psychosis/schizophrenia: human studies. European Archives of Psychiatry Clinical Neuroscience 2009;259(7):413‐31. - PMC - PubMed
Davison 1972
    1. Davison K, Wilson H. Psychosis associated with cannabis smoking. Addiction 1972;67(3):225‐8. - PubMed
Deeks 2000
    1. Deeks J. Issues in the selection for meta‐analyses of binary data. Abstracts of 8th International Cochrane Colloquium; 2000 Oct 25‐28th; Cape Town, South Africa. 2000.
Divine 1992
    1. Divine GW, Brown JT, Frazer LM. The unit of analysis error in studies about physicians' patient care behavior. Journal of General Internal Medicine 1992;7:623‐9. - PubMed
Dixon 1990
    1. Dixon L, Haas G, Wedien PJ, Sweeney J, Frances AJ. Acute effects of drug abuse in schizophrenic patients: clinical observations and patients' self‐reports. Schizophrenia Bulletin 1990;16:69‐79. - PubMed
Donner 2002
    1. Donner A, Klar N. Issues in the meta‐analysis of cluster randomised trials. Statistics in Medicine 2002;21:2971‐80. - PubMed
Duke 2001
    1. Duke PJ, Pantelis C, McPhillips MA, Barnes TR. Comorbid non‐alcohol substance misuse among people with schizophrenia: epidemiological study in central London. British Journal of Psychiatry 2001;179:509‐13. - PubMed
Egger 1997
    1. Egger M, Davey G, Schneider M, Minder C. Bias in meta‐analysis detected by a simple, graphical test. BMJ 1997;315:629‐34. - PMC - PubMed
Elbourne 2002
    1. Elbourne D, Altman DG, Higgins JPT, Curtina F, Worthingtond HV, Vaile A. Meta‐analyses involving cross‐over trials: methodological issues. International Journal of Epidemiology 2002;31(1):140‐9. - PubMed
EMCDDA
    1. An overview of drug potency in Europe. European Monitoring Centre for Drugs and Drug Addiction.
Farrell 1998
    1. Farrell M, Howes C, Taylor C. Substance misuse of psychiatric co‐morbidity: an overview of the OPCS National Psychiatric Morbidity Survey. Addictive Behavior 1998;23:908‐18. - PubMed
Franken 2002
    1. Franken IH, Hendriks VM, Brink W. Initial validation of two opiate craving questionnaires the obsessive compulsive drug use scale and the desires for drug questionnaire.. Addictive Behaviors, 2002;27(5):675‐85. - PubMed
Freund 2003
    1. Freund TF, Katona I, Piomelli D. Role of endogenous cannabinoids in synaptic signalling. Physiological reviews Jul 2003;83(3):1017‐66. - PubMed
Furukawa 2006
    1. Furukawa TA, Barbui C, Cipriani A, Brambilla P, Watanabe N. Imputing missing standard deviations in meta‐analyses can provide accurate results. Journal of Clinical Epidemiology 2006;59(7):7‐10. - PubMed
Gaoni 1964
    1. Gaoni Y, Mechoulam R. Isolation, structure, and partial synthesis of an active constituent of hashish. Journal of the American Chemical Society 1964;86:1646‐7.
Goldman 1992
    1. Goldman HH, Skodol AE, Lave TR. Revising axis V for DSM‐IV: a review of measures of social functioning. American Journal of Pschiatry 1992;149:1148‐56. - PubMed
Gulliford 1999
    1. Gulliford MC, Ukoumunne OC, Chinn S. Components of variance and intraclass correlations for the design of community‐based surveys and intervention studies: data from the Health Survey for England 1994. American Journal of Epidemiology 1999;149:876‐83. - PubMed
Hall 1999
    1. Hall W, Johnston L, Donnelly N. The Health Effects of Cannabis. 1st Edition. Toronto: Toronto: Additction Research Foundation, 1999.
Hambrecht 2000
    1. Hambrecht M, Häfner H. Cannabis, vulnerability, and the onset of schizophrenia: an epidemiological perspective. Australian and New Zealand Journal of Psychiatry 2000;34(3):468‐75. - PubMed
Heishman 2006
    1. Heishman SJ, Singleton EG. Assessment of cannabis craving using the Marijuana Craving Questionnaire. Methods in Molecular Medicine 2006;123:209‐16. - PubMed
Henquet 2005
    1. Henquet C, Krabbendam L, Spauwen J, Kaplan C, Lieb R, Wittchen HU, et al. Prospective cohort study of cannabis use, predisposition for psychosis, and psychotic symptoms in young people. BMJ 2005;330(11):7481. - PMC - PubMed
Henquet 2008
    1. Henquet C, Forti M, Morrison P, Kuepper R, Murray RM. Gene‐environment interplay between cannabis and psychosis. Schizophrenia Bulletin 2008;34(6):1111‐21. - PMC - PubMed
Hides 2006
    1. Hides L, Dawe S, Kavanagh DJ, Young RM. Psychotic symptom and cannabis relapse in recent‐onset psychosis. Prospective study. British Journal of Psychiatry 2006;189:137‐43. - PubMed
Higgins 2003
    1. Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta‐analyses. BMJ 2003;327:557‐60. - PMC - PubMed
Higgins 2006
    1. Higgins JPT. Cochrane Handbook for Systematic Reviews of Interventions 4.2.6 [updated September 2006]. In: Higgins JPT, Green S editor(s). The Cochrane Library. Chichester, UK: John Wiley & Sons, Ltd., 2006.
Higgins 2011
    1. Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.2 [updated September 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane‐handbook.org.
Hogan 1983
    1. Hogan TP, Awad AG, Eastwood R. A self‐report scale predictive of drug compliance in schizophrenics: reliability and discriminative validity. Psychological Medicine Feb 1983;13(1):177‐83. - PubMed
Hunt 2013
    1. Hunt GE, Matheson SL, Siegfried N, Walter G, Cleary M. Psychosocial interventions for people with both severe mental illness and substance misuse. Cochrane Database of Systematic Reviews 2013, Issue 10. [DOI: 10.1002/14651858.CD001088.pub3] - DOI - PubMed
Isbell 1967
    1. Isbell H, Gorodetsky CW, Jasinski D, Claussen U, Spulak F, Korte F. Effects of 9‐trans‐tetrahydrocannabinol in man. Psychophormacologia 1967;11:184. - PubMed
Jablensky 1992
    1. Jablensky A, Sartorius N, Ernberg G, Anker, M. Schizophrenia: manifestations, incidence and course in different cultures: A World Health Organization ten‐country study. Psychological Medicine 1992;Suppl 20:97. - PubMed
Kavanagh 2004
    1. Kavanagh DJ, Waghorn G, Jenner L, Chant DC, Carr V, Evans M, et al. Demographic and clinical correlates of comorbid substance use disorders in psychosis: multivariate analyses from an epidemiological sample. Schizophrenia Research 2004;66(2‐3):115‐24. - PubMed
Kay 1986
    1. Kay SR, Opler LA, Fiszbein A. Positive and negative syndrome scale (PANSS) manual. North Tonawanda (NY): Multi‐Health Systems, 1986.
Kay 1987
    1. Kay SR, Fiszbein A, Opler LA. The positive and negative syndrome scale (PANSS) for schizophrenia. Schizophrenia Bulletin 1987;13(2):261‐76. - PubMed
Kolliakou 2011
    1. Kolliakoua A, Joseph C, Ismail K, Atakan Z, Murray RM. Why do patients with psychosis use cannabis and are they ready to change their use?. Neuroscience May 2011;29(3):335‐46. - PubMed
Kouri 1999
    1. Kouri EM, Harrison G, Pope G Jnr. Changes in aggressive behavior during withdrawal from long term marijuana use. Psychopharmacology 1999;143:302‐8. - PubMed
Leucht 2005
    1. Leucht S, Kane JM, Kissling W, Hamann J, Etschel E, Engel RR. What does the PANSS mean?. Schizophrenia Research 2005;79(2‐3):231‐8. [PUBMED: 15982856] - PubMed
Leucht 2005a
    1. Leucht S, Kane JM, Kissling W, Hamann J, Etschel E, Engel R. Clinical implications of Brief Psychiatric Rating Scale Scores. British Journal of Psychiatry 2005;187:366‐71. - PubMed
Leucht 2007
    1. Leucht S, Engel RR, Bauml J, Davis JM. Is the superior efficacy of new generation antipsychotics an artefact of LOCF?. Schizophrenia Bulletin 2007;33(1):183‐91. [PUBMED: 16905632] - PMC - PubMed
Leweke 1999
    1. Leweke FM, Guiffrida A, Wurster U, Emrich HM, Piomelli D. Elevated endogenous cannabinoids in schizophrenia. Neuroreport 1999;10:1665‐69. - PubMed
Linszman 1994
    1. Linszman DH, Dingemans PM, Lenoir ME. Cannabis abuse and the course of recent onset schizophrenic disorders. Archives of General Adult Psychiatry 1994;51:273‐9. - PubMed
Lishman 1998
    1. Lishman WA. Organic Psychiatry: The Psychological Consequences of Cerebral Disorder. 3rd Edition. Oxford: Blackwell, 1998.
Littlewood 1988
    1. Littlewood R. Ideology, camouflage or contingency? Racism in British psychiatry. Transcultural Psychiatry 1988;30(3):243‐90.
Lynskey 2002
    1. Lynskey MT, Heath AC, Nelson EC, Bucholz KK, Madden PA, Slutske WS, et al. Genetic and environmental contributions to cannabis dependence in a national young adult twin sample. Psychological Medicine 2002;32(2):195‐207. - PubMed
Marshall 2000
    1. Marshall M, Lockwood A, Adams C, Bradley C, Joy C, Fenton M. Unpublished rating scales ‐ a major source of bias in randomised controlled trials of treatments for schizophrenia?. British Journal of Psychiatry 2000;176:249‐52. - PubMed
Matheson 2011
    1. Matheson SL, Shepherd AM, Laurens KR, Carr VJ. A systematic meta‐review grading the evidence for non‐genetic risk factors and putative antecedents of schizophrenia. Schizophrenia Research 2011;133(1‐3):133‐42. - PubMed
McGovern 1987
    1. McGovern D, Cope R. First admission rates of first and second generation Afro‐Caribbeans. Journal of Social Distress and the Homeless 1987;22:139‐48. - PubMed
McLellan 1980
    1. Mclellan A, Luborsky T, Woody L, O'Brien GE, Charles P. An improved diagnostic evaluation instrument for substance abuse patients. The Addiction Severity Index. Journal of Nervous and Mental Disease 1980;168(1):26‐33. - PubMed
Miles 2001
    1. Miles DR, Bree MB, Gupman AE, Newlin DB, Glantz MD, Pickens RW. A twin study on sensation seeking, risk taking behavior and marijuana use. Drug and Alcohol Dependence 2001;62:57‐68. - PubMed
Moher 2001
    1. Moher D, Schulz KF, Altman D. The CONSORT statement: revised recommendations for improving the quality of reports of parallel‐group randomised trials. JAMA 2001;285(15):1987‐91. - PubMed
Moore 2007
    1. Moore TH, Zammit S, Lingford‐Hughes A, Barnes TR, Jones PB, Burke M, et al. Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review. Lancet 2007;370(9584):319‐28. - PubMed
Negrete 1986
    1. Negrete JC, Knapp WP, Douglas DE, Smith WB. Cannabis affects the severity of schizophrenic symptoms: results of a clinical survey. Psychological Medicine 1986;16:515‐20. - PubMed
Nunez 2002
    1. Nunez LA, Gurpegui M. Cannabis‐induced psychosis: a cross‐sectional comparison with acute schizophrenia. Acta Psychiatrica Scandinavica 2002;105:173‐8. - PubMed
Overall 1988
    1. Overall JE, Gorham DR. The Brief Psychiatric Rating Scale (BPRS): Recent developments in ascertainment and scaling. Psychopharmacology Bulletin 1988;24:97‐9. - PubMed
Regier 1990
    1. Regier DA, Farmer ME, Rae DS. Co‐morbidity of mental disorders with alcohol and other drug abuse: results from the Epidemiologic Catchment Area (ECA) study. JAMA 1990;264:2511‐8. - PubMed
Russo 2008
    1. Russo EB, Jiang HE. Phytochemical and genetic analyses of ancient cannabis from Central Asia. Journal of Experimental Botany 2008;59(15):4171‐82. - PMC - PubMed
Schulz 1995
    1. Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias: dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA 1995;273:408‐12. - PubMed
Schunemann 2008
    1. Schunemann HJ, Oxman AD, Vist GE, Higgins JPT, Deeks JJ, Glasziou P, et al. Chapter 12: Interpreting results and drawing conclusions. In: Higgins JPT, Green S editor(s). Cochrane Handbook for Systematic Reviews of Interventions. The Cochrane Collaboration, 2008:359‐83.
Semple 2005
    1. Semple DM, McIntosh AM, Lawrie SM. Cannabis as a risk factor for psychosis: systematic review. Journal of Psychopharmacology 2005;19(2):187‐94. - PubMed
Simpson 1970
    1. Simpson GM, Angus JWS. A rating scale for extrapyramidal side effects. Acta Psychiatrica Scandinavica 1970;212:11‐9. - PubMed
Sinclair 2008
    1. Sinclair J. Co‐morbid substance misuse in psychiatric patients: prevalence and association with length of inpatient stay. Journal of Psychopharmacology 2008;22(1):92‐9. - PubMed
Smith 1994
    1. Smith J, Hucker S. Schizophrenia and substance abuse. British Journal of Psychiatry 1994;165:13‐21. - PubMed
Sobell 1992
    1. Sobell LC, Sobell MB. Timeline Follow‐back: A technique for assessing self‐reported ethanol consumption. In: In J. Allen, R. Z. Litten (Eds.) editor(s). Measuring Alcohol Consumption: Psychosocial and Biological Methods. Totowa, NJ: Humana Press, 1992:41‐72.
Soyka 1993
    1. Soyka M, Immler B, Sand P. Alcohol and drug abuse as risk factors for violence and delinquency in schizophrenic patients. Psychiatrische Praxis 1993;5:172‐5. - PubMed
Stephens 1993
    1. Stephens RS, Roffman RA, Simpson EE. Adult marijuana users seeking treatment. Journal of Consulting and Clinical Psychology 1993;62:1100‐4. - PubMed
Talbot 1969
    1. Talbot JA, Teague JW. Marihuana psychosis. Acute toxic psychosis associated with the use of Cannabis derivatives. JAMA 1969;210(2):299‐302. - PubMed
Tanda 1997
    1. Tanda G, Pontiere FE, DiChiara G. Cannabinoid and heroin activation of mesolimbic dopamine transmission by a common mu1 opioid receptor mechanism. Science 1997;276:2048‐50. - PubMed
Thomas 1996
    1. Thomas H. A community survey of adverse effects of cannabis use. Drug and Alcohol Dependence 1996;42:201‐7. - PubMed
Tunving 1985
    1. Tunving K. Psychiatric effects of cannabis use. Acta Psychiatrica Scandinavica 1985;72:209‐17. - PubMed
Ukoumunne 1999
    1. Ukoumunne OC, Gulliford MC, Chinn S, Sterne JAC, Burney PGJ. Methods for evaluating area‐wide and organisation‐based intervention in health and health care: a systematic review. Health Technology Assessment 1999;3(5):1‐75. - PubMed
UNODOC
    1. UNODC. World Drug Report 2012. United Nations publication Vol. 12, issue XI:1.
Van Os 2002
    1. Os J, Bak M, Hanssen M, Bijl RV, Graaf R, Verdoux H. Cannabis use and psychosis: A longitudinal population‐based study. American Journal of Epidemiology 2002;156:319‐27. - PubMed
Varma 1972
    1. Varma LP. Cannabis psychosis. Indian Journal of Psychiatry 1972;14:241‐55.
Virgo 2001
    1. Virgo N, Bennett G, Higgins D, Bennett L, Thomas P. The prevalence and characteristics of co‐occurring serious mental illness (SMI) and substance abuse or dependence in the patients of Adult Mental Health and Addictions Services in eastern Dorset. Journal of Mental Health 2001;10(2):175‐88.
Warner 1994
    1. Warner R. Recovery from Schizophrenia: Psychiatry and Political Economy. Psychology Press 1994.
Warnock 1903
    1. Warnock J. Insanity from Hasheesh. Journal of Mental Sciences 1903;49:96‐110.
WHOQOL
    1. WHOQOL. WHOQOL ‐ Brief introduction, administration,scoring and generic version of the assessment. WHO December 1996.
Wing 1990
    1. Wing JK, Barbo T, Brugha T, Burke J, Cooper J, Giel R, et al. Schedules for Clinical Assessment in Neuropsychiatry. Archives of General Psychiatry 1990;47:589‐93. - PubMed
Xia 2009
    1. Xia J, Adams CE, Bhagat N, Bhagat V, Bhoopathi P, El‐Sayeh H, et al. Loss to outcomes stakeholder survey: the LOSS study. Psychiatric Bulletin 2009;33(7):254‐7.
Zammit 2002
    1. Zammit S, Allebeck P, Andreasson S, Lundberg I, Lewis G. Self reported cannabis use as a risk factor for schizophrenia in Swedish conscripts of 1969: historical cohort study. BNJ 2002;325:1199‐201. - PMC - PubMed

References to other published versions of this review

Rathbone 2008
    1. Rathbone J, Variend H, Mehta H. Cannabis and schizophrenia. Cochrane Database of Systematic Reviews 2008, Issue 3. [DOI: 10.1002/14651858.CD004837.pub2] - DOI - PMC - PubMed

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