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. Author manuscript; available in PMC: 2015 Jun 1.
Published in final edited form as: Curr Addict Rep. 2014 Jun 1;1(2):115–128. doi: 10.1007/s40429-014-0018-7

Table 2. Studies of the Genetic × Cannabis Interaction.

Gene/locus Study Study Design Sample Size Follow up Results
COMT/rs4680 Caspi et al 2005 Longitudinal, prospective (Dunedin cohort) 803 26 years OR of developing psychotic disorder:

  • 10.9 (2.2-54.1, 95% CI) for Val/Val genotype

  • 2.5 (0.78-8.2, 95% CI) for Val/Met allele

  • 1.1 (0.21-5.4, 95% CI) for Met/Met allele
COMT/rs4680 Zammit, Owens et al 2011 Longitudinal (Avon cohort) 2630 2 years OR of psychosis in cannabis users:

  • 1.56 (1.05-2.31, 95% CI) with Met/Met genotype

  • 1.47(0.85-2.26, 95% CI) with Val/Val genotype

  • 1.68 (1.23-2.28, 95% CI) with Met/Val genotype
OR 1.0 (0.73-1.36, 95% CI) of cannabis x COMT interaction
COMT/rs4680 Costas et al 2011 Case-only, cross-sectional analysis 748 NA OR 2.07 (1.27-3.26, 95% CI) of history of cannabis use in schizophrenia patients with Met/Met genotype v. Val/Val genotype
COMT/rs4680 Estrada et al2011 Case-control, cross-sectional analysis 80 inpatients with schizophrenia NA No difference in genotypes between diagnosis groups or between cannabis users and non-users
77 inpatients with non-psychotic psychiatric illness AOP was 15.46 (SD 1.09) for Val/Val cannabis users
AOP was 17.12 (SD 2.9) for Val/Met cannabis users
AOP was 18.78 (4.01) for Met/Met cannabis users
For effect of genotype on AOP, beta = 1.66, SE = 0.78, p = 0.04
AKT1/rs2494732 van Winkel 2011 Cross-sectional analysis 801 subjects with psychosis NA RR 1.90 (p < 0.01) of C/C genotype in daily cannabis users - Case-only analysis
740 unaffected Siblings OR 1.96 (1.09-3.53, 95% CI) of being diagnosed with psychotic disorder in C/C allele subjects - Case-sibling analysis
419 controls OR 2.08 (0.92-4.67, 95% CI) of being diagnosed with psychotic disorder in C/C allele subjects - Case-control analysis
AKT1/rs2494732 DiForte et al 2012 Case-control, cross-sectional analysis 489 subjects NA OR 7.23 (1.37-38.12, 95% CI) of psychotic disorder in C/C genotype subjects with daily cannabis use v. T/T genotype
278 controls OR 2.18 (1.12-4.31, 95% CI) of psychotic disorder in C/C genotype subjects with history of cannabis use

OR = odds ratio; RR = relative risk; CI = confidence interval; AOP = age of onset of psychosis; SE = standard error