The number of cannabis smokers is increasing. Between 1999 and 2001, the number of 14-15 year olds who had tried cannabis rose from 19% to 29% in boys and 18% to 25% in girls. A Home Office document estimates that 3.2 million people in Britain smoke cannabis.
Regular use of cannabis is associated with an increased risk of mental illnesses, such as schizophrenia and depression. Smoking cannabis also causes chronic bronchitis, emphysema, and other lung disorders, often in young people. There are also reports of lung, tongue, and other cancers in cannabis smokers.
Despite these alarming facts, there is no evidence at present on whether smoking cannabis contributes to the progression of coronary artery disease, as smoking cigarettes does. More studies of the effects of cannabis are essential, say the authors.
One could calculate that if cigarettes cause an annual excess of 120,000 deaths among 13 million smokers, deaths among 3.2 million cannabis smokers would be 30,000, assuming equity of effect, they write. Even if the number of deaths attributable to cannabis turned out to be a fraction of that figure, smoking cannabis would still be a major public health hazard.
When the likely mental health burden is added, these signals cannot be ignored, they conclude.