RESEARCH - Cannabis smoking contributes to pulmonary disease

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Cannabis smoking contributes to pulmonary disease

By Reuters Health

December 13, 2007

NEW YORK (Reuters Health), Dec 13 - Long-term cannabis smoking significantly

impairs the function of large airways, according to a report in the December

issue of Thorax, which also found that one cannabis cigarette has the

adverse effects of up to five tobacco cigarettes.

" Habitual use of cannabis may cause asthma and chronic bronchitis, " Dr.

Beasley from Medical Research Institute of New Zealand, Wellington,

told Reuters Health. " The current initiatives to reduce tobacco smoking

should also include attempts to reduce cannabis smoking. "

Dr. Beasley, the principal study investigator, and associates used lung

function tests, high-resolution CT scans, and detailed questionnaires to

determine the association between cannabis smoking (with or without tobacco)

on pulmonary structure, function, and symptoms in 339 subjects.

Cannabis smoking was associated with an increased risk of wheeze, chest

tightness, and cough, the authors report, whereas tobacco smoking was

associated with a similarly increased risk of wheeze and cough.

Cannabis smokers had twice the risk of chronic bronchitis and a 70%

increased risk of asthma diagnosed after age 16 years.

Cannabis and tobacco smoking were both associated with a reduction in the

FEV1/FVC ratio, but only tobacco smoking reduced FEV1 and maximum

mid-expiratory flow.

An increased percentage of low density lung tissue was associated with

cannabis smoking, but not with tobacco smoking.

Macroscopic emphysema was associated with tobacco smoking (but not with

cannabis smoking), the researchers note.

Based on the changes in pulmonary function test results, the investigators

calculated that one joint was pathologically equivalent to 2.5 to 5 tobacco

cigarettes.

" In terms of counseling patients, advice can be given that long-term

cannabis smoking increases the risk of lung damage, causing both asthma and

chronic bronchitis, " Dr. Beasley said. " The most important finding for

patients is that one cannabis joint causes a similar degree of lung damage

as up to five tobacco cigarettes -- this provides patients with a good

measure of the relative risks of cannabis and tobacco smoking. "

" Although we know far less about the effect of cannabis on the lung than the

effects of tobacco smoking, (this study) confirms that cannabis smoking

constitutes a substantial hazard to the lung, " comments Dr. Lange from

Hvidovre Hospital, Copenhagen, in a related editorial.

By Will Boggs, M.D.

Last Updated: 2007-12-13 11:32:18 -0400 (Reuters Health)

Thorax 2007;62:1036-1037,1058-1063.

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