14 August 2019

A systematic review of the association between cannabis use and the risk of tuberculosis (TB) led by the NIHR Health Protection Research Unit in Evaluation of Interventions at the University of Bristol has been published in BMC Public Health. The review indicates a potential link between cannabis use and TB but highlights that the evidence base is limited in both quantity and quality. There is a need for more high-quality primary research on the topic.

An estimated 1.7 billion people globally are infected with TB, 5-15% of whom will go on to develop active TB disease. In high-income settings TB most commonly occurs in marginalised populations such as migrants, the homeless, people who inject drugs and prisoners.

In a recent TB outbreak in the United Kingdom, 26% of those with latent TB infection and 67% with active TB disease reported cannabis smoking. Public Health England identified a need to better understand whether there is an association between cannabis use and TB. Since cannabis is estimated to be the most widely used (largely) illegal substance in Western countries, this is potentially a significant public health concern.

Researchers from the NIHR Health Protection Research Unit in Evaluation of Interventions at the University of Bristol conducted a systematic review of the evidence. A range of electronic databases together with key websites and conference proceedings were searched. Two authors independently screened studies for inclusion and extracted relevant data. The quality of individual studies included in the review was formally assessed.  

Based on the small number of available studies on the topic (n=11) authors found some evidence for an association between cannabis use and latent TB infection, but little evidence for an association with active TB disease. The quality of the available studies was, however, low and the findings should therefore be interpreted with caution.

Lead researchers, Dr Clare French (University of Bristol) and Dr Caroline Coope (Public Health England) said “Although it is difficult to draw firm conclusions on the association between cannabis use and TB based on the data available, which is limited in both quantity and quality, there is some evidence of a link. Further, robust primary research on the topic is required. This information is important to inform ongoing and future TB prevention and control strategies”.

Professor Isabel Oliver (Public Health England) said: “Although we have seen a reduction in TB infections in England since 2011, TB remains an important public health problem. Studies like this are key to help us understand risk and control infection. This information is useful to inform our strategies towards elimination of TB in England by 2035.”

Paper: Cannabis use and the risk of tuberculosis: a systematic review by Clare E. French, Caroline M Coope, Luke A. McGuiness, Charles R. Beck, Sophie Newitt, Lauren Ahhyow, Matt Hickman and Isabel Oliver. Published in BMC Public Health. 27 July 2019.

Further information

About the NIHR HPRU in Evaluation of Interventions at the University of Bristol

The Health Protection Research Unit (HPRU) in Evaluation of Interventions, based in Population Health Sciences at the University of Bristol, is part of the National Institute for Health Research (NIHR) and a partnership between University of Bristol and Public Health England (PHE), in collaboration with University College London, Cambridge Medical Research Council (MRC) Biostatistics Unit and University of the West of England. We are a multidisciplinary team undertaking applied research on the development and evaluation of interventions to protect the public’s health. Our aim is to support PHE in delivering its objectives and functions. Our focus is on the PHE priority area of infection. Follow us on Twitter: @HPRU_EI