Report warns of dangers of cannabis and general ignorance

Ignorance about the dangers of cannabis has been revealed this week in a new report from the British Lung Foundation, ‘The Impact of Cannabis on your Lungs’ (PDF). Perceived as less dangerous than tobacco by most users and as harmless by one in three, cannabis smoking carries a twenty-times greater risk of lung cancer than tobacco smoking, it warns, and yet a third of people aged under 24 in the UK use it.

The report, which gives an overview of current evidence on the impact of cannabis smoking on lung health, highlights the strong associations with many lung and respiratory illnesses, including tuberculosis, acute bronchitis and lung cancer. It is also strongly associated with suppression of the immune system, heart disease and mental health problems.

So what can be done to discourage people from using cannabis and other ‘recreational’ drugs? Schools are one setting for drugs education, of course, and in the UK this is taught as part of the National Curriculum, but what about non-school settings?

A Cochrane review looked at the effectiveness of interventions to prevent or reduce drug use in under 25s delivered away from schools, at drop-in centres, community workshops and evening classes for example. Seventeen randomised controlled trials were suitable for inclusion; all but two of the studies conducted in the USA, the others in the UK and China. Follow-up periods varied from at completion of the intervention to six years. The studies varied too widely for results to be combined. Here’s what they found:

  • One study of motivational interviewing suggested that this intervention was beneficial on cannabis use
  • Three family interventions (Focus on Families, Iowa Strengthening Families Program and Preparing for the Drug-Free Years), each evaluated in one study, suggested that they may be beneficial in preventing cannabis use
  • Multi-component community interventions and group education and skills training were not shown to be effective


  •  Many studies had methodological drawbacks
  • There were too few studies for firm conclusions
  • None of the studies evaluated costs

The authors concluded:

“There is a lack of evidence of effectiveness of the included interventions. Motivational interviewing and some family interventions may have some benefit. Cost-effectiveness has not yet been addressed in any studies, and further research is needed to determine whether any of these interventions can be recommended.”

The British Lung Foundation also calls for more research, further investigating the impact of cannabis on respiratory health, and for public health education programmes to be implemented to dispel the myth that smoking cannabis is relatively safe.


British Lung Foundation. New report reveals dangerous lack of public understanding of the health risks of cannabis. 6 June 2012.

Gates S, McCambridge J, Smith LA, Foxcroft D. Interventions for prevention of drug use by young people delivered in non-school settings. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD005030. DOI: 10.1002/14651858.CD005030.pub2.

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Sarah Chapman

My name is Sarah Chapman. I have worked on systematic reviews and other types of research in many areas of health for the past 17 years, for the Cochrane Collaboration and for several UK higher education institutions including the University of Oxford and the Royal College of Nursing Institute. I also have a background in nursing and in the study of the History of Medicine.

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