High prevalence of cannabis use among Aka foragers of the Congo Basin and its possible relationship to helminthiasis

Am J Hum Biol. 2016 Jan-Feb;28(1):5-15. doi: 10.1002/ajhb.22740. Epub 2015 May 29.


Objectives: Little is known about cannabis use in hunter-gatherers. Therefore, we investigated cannabis use in the Aka, a population of foragers of the Congo Basin. Because cannabis contains anthelminthic compounds, and the Aka have a high prevalence of helminthiasis, we also tested the hypothesis that cannabis use might be an unconscious form of self-medication against helminths.

Methods: We collected self- and peer-reports of cannabis use from all adult Aka in the Lobaye district of the Central African Republic (n = 379). Because female cannabis use was low, we restricted sample collection to men. Using an immunoassay for Δ9-tetrahydrocannabinol-11-oic acid (THCA), a urinary biomarker of recent cannabis consumption, we validated cannabis use in men currently residing in camps near a logging road (n = 62). We also collected stool samples to assay worm burden. A longitudinal reinfection study was conducted among a subsample of the male participants (n = 23) who had been treated with a commercial anthelmintic 1 year ago.

Results: The prevalence of self- and peer-reported cannabis use was 70.9% among men and 6.1% among women, for a total prevalence of 38.6%. Using a 50 ng/ml threshold for THCA, 67.7% of men used cannabis. Cannabis users were significantly younger and had less material wealth than the non-cannabis users. There were significant negative associations between THCA levels and worm burden, and reinfection with helminths 1 year after treatment with a commercial anthelmintic.

Conclusions: The prevalence of cannabis use among adult Aka men was high when compared to most global populations. THCA levels were negatively correlated with parasite infection and reinfection, supporting the self-medication hypothesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Anthelmintics / administration & dosage*
  • Biomarkers / urine
  • Central African Republic / epidemiology
  • Dronabinol / analogs & derivatives*
  • Dronabinol / urine
  • Helminthiasis / epidemiology*
  • Helminthiasis / parasitology
  • Humans
  • Immunoassay
  • Longitudinal Studies
  • Male
  • Marijuana Smoking / epidemiology*
  • Marijuana Smoking / urine
  • Middle Aged
  • Prevalence
  • Self Report
  • Socioeconomic Factors
  • Young Adult


  • Anthelmintics
  • Biomarkers
  • 11-nor-delta(9)-tetrahydrocannabinol-9-carboxylic acid
  • Dronabinol