Increasing Delta-9-Tetrahydrocannabinol (Δ-9-THC) Content in Herbal Cannabis Over Time: Systematic Review and Meta-Analysis
Methods: Systematic searches of 17 electronic scientific databases identified studies on this topic, within which 21 case series studies satisfied our inclusion criteria of reporting the mean tetrahydrocannabinol (THC) value per number of samples per year. No language, publication date, publication type or status restrictions were imposed. The study selection and data extraction processes were performed independently but uniformly by two authors, included screening, determination of eligibility and inclusion of the eligible studies in the systematic review, and a meta-analysis of the results on THC content in herbal cannabis samples. We considered papers and not monographic scientific publications, rejecting all studies that were not focused on the subject of this review.
Results: Meta-analysis by year was performed on 21 studies containing 75 total mean THC observations from 1979 to 2009 using the random effects model. The results revealed much variability between studies. Further, there was a significant correlation between year and mean THC in herbal cannabis. The combined data indicated the correlation between year and mean THC in herbal cannabis, revealing a temporal trend of increasing potency (5% above the mean THC value in the Poisson regression analysis).
Conclusions: The results of the analysis suggest that there has been a recent and consistent increase in cannabis potency worldwide.
Document Type: Research Article
Publication date: 2012-03-01
Current Drug Abuse Reviews aims to publish the highest quality reviews, meta-analyses and drug clinical trial studies on all latest advances on alcohol and drug abuse and addiction.
Book reviews are also published. The Journal will further comprise an agenda listing relevant meetings and conferences that will take place in near future, and advertisement.
- Editorial Board
- Information for Authors
- Subscribe to this Title
- Ingenta Connect is not responsible for the content or availability of external websites