Genetic and environmental influences on cannabis use initiation and problematic use: a meta-analysis of twin studies
Article first published online: 5 FEB 2010
© 2010 The Authors. Journal compilation © 2010 Society for the Study of Addiction
Volume 105, Issue 3, pages 417–430, March 2010
How to Cite
Verweij, K. J. H., Zietsch, B. P., Lynskey, M. T., Medland, S. E., Neale, M. C., Martin, N. G., Boomsma, D. I. and Vink, J. M. (2010), Genetic and environmental influences on cannabis use initiation and problematic use: a meta-analysis of twin studies. Addiction, 105: 417–430. doi: 10.1111/j.1360-0443.2009.02831.x
- Issue published online: 5 FEB 2010
- Article first published online: 5 FEB 2010
- Submitted 11 June 2009; initial review completed 20 August 2009; final version accepted 24 September 2009
- twin research
Background Because cannabis use is associated with social, physical and psychological problems, it is important to know what causes some individuals to initiate cannabis use and a subset of those to become problematic users. Previous twin studies found evidence for both genetic and environmental influences on vulnerability, but due to considerable variation in the results it is difficult to draw clear conclusions regarding the relative magnitude of these influences.
Methods A systematic literature search identified 28 twin studies on cannabis use initiation and 24 studies on problematic cannabis use. The proportion of total variance accounted for by genes (A), shared environment (C) and unshared environment (E) in (i) initiation of cannabis use and (ii) problematic cannabis use was calculated by averaging corresponding A, C and E estimates across studies from independent cohorts and weighting by sample size.
Results For cannabis use initiation, A, C and E estimates were 48%, 25% and 27% in males and 40%, 39% and 21% in females. For problematic cannabis use A, C and E estimates were 51%, 20% and 29% for males and 59%, 15% and 26% for females. Confidence intervals of these estimates are considerably narrower than those in the source studies.
Conclusions Our results indicate that vulnerability to both cannabis use initiation and problematic use was influenced significantly by A, C and E. There was a trend for a greater C and lesser A component for cannabis use initiation compared to problematic use for females.