April 3, 1997

April 3, 1997, Los Angeles, CA: Habitual marijuana smokers do not experience a greater annual rate of decline in lung function than nonsmokers, according to the latest findings by researchers at the University of California at Los Angeles (UCLA) School of Medicine.

The results of the eight-year study appear in Volume 155 of the American Journal of Respiratory & Critical Care Medicine. Dr. Donald P. Tashkin, who headed the study, is one of America's foremost experts on marijuana smoking and lung function.

"Findings from the present long-term, follow-up study of heavy, habitual marijuana smokers argue against the concept that continuing heavy use of marijuana is a significant risk factor for the development of [chronic lung disease]," concluded the UCLA study. "Neither the continuing nor the intermittent marijuana smokers exhibited any significantly different rates of decline in [lung function]" as compared with those individuals who never smoked marijuana.

Researchers added: "No differences were noted between even quite heavy marijuana smoking and nonsmoking of marijuana." These findings starkly contrasted those experienced by tobacco-only smokers who suffered a significant rate of decline in lung function.

Researchers also failed to find any synergistic effect between marijuana and tobacco cigarettes. According to the report, individuals who smoked both did not suffer any faster rate of decline in lung function than individuals who smoked marijuana alone.

A total of 394 young Caucasian men and women agreed to participate in the study. Researchers classified 131 of the participants as heavy marijuana smokers who did not smoke tobacco cigarettes, while 112 smoked both tobacco and marijuana. An additional 65 men regularly smoked tobacco only and the remaining 86 participants were nonsmokers. All participants were screened for pre-existing chronic chest diseases and found to be healthy upon entering the study.

Each participant underwent pulmonary function testing at the start of the study, and again on multiple occasions over the course of the next eight years. During that interval, a number of patients were lost to follow up, but 255 participants (65 percent) completed the study and were tested again at up to six additional sessions.

The results of this latest long-term study on marijuana and health echo findings reached by an Australian group of researchers at the National Drug and Alcohol Research Centre just one month ago. That study, which involved interviews with 268 marijuana smokers and 31 non-using partners and family members, concluded that the health of long-term marijuana users is virtually no different from that of the general population.

Researchers from both studies cautioned that their results do not imply that regular marijuana smoking is free of all potentially harmful pulmonary effects. Both groups stated that regular marijuana smokers were more likely to suffer mild respiratory problems such as wheezing and bronchitis than nonsmokers.

A summary of the UCLA study appears in the March 1997 edition of Forensic Drug Abuse Advisor.

Imperial College London, Press Release, 3rd September 2005

DP Tashkin, MS Simmons, DL Sherrill and AH Coulson
Department of Medicine, UCLA Schools of Medicine and Public Health, Los Angeles, CA 90095-1690, USA.

To assess the possible role of daily smoking of marijuana in the development of chronic obstructive pulmonary disease (COPD), we evaluated the effect of habitual use of marijuana with or without tobacco on the age-related change in lung function (measured as FEV1) in comparison with the effect of nonsmoking and regular tobacco smoking. A convenience sample of 394 healthy young Caucasian adults (68% men; age: 33 +/- 6 yr; mean +/- SD) including, at study entry, 131 heavy, habitual smokers of marijuana alone, 112 smokers of marijuana plus tobacco, 65 regular smokers of tobacco alone, and 86 nonsmokers of either substance were recruited from the greater Los Angeles community.

FEV1 was measured in all 394 participants at study entry and in 255 subjects (65 %) on up to six additional occasions at intervals of > or = 1 yr (1.7 +/- 1.1 yr) over a period of 8 yr. Random-effects models were used to estimate mean rates of decline in FEV1 and to compare these rates between smoking groups. Although men showed a significant effect of tobacco on FEV1 decline (p < 0.05), in neither men nor women was marijuana smoking associated with greater declines in FEV1 than was nonsmoking, nor was an additive effect of marijuana and tobacco noted, or a significant relationship found between the number of marijuana cigarettes smoked per day and the rate of decline in FEV1. We conclude that regular tobacco, but not marijuana, smoking is associated with greater annual rates of decline in lung function than is nonsmoking.

These findings do not support an association between regular marijuana smoking and chronic COPD but do not exclude the possibility of other adverse respiratory effects.

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April 13, 2009 -- People who smoke both cigarettes and marijuana have a greater risk for developing the progressive lung disease COPD than cigarette smokers who don't smoke pot, a new study shows.

Smokers in the study who reported using both tobacco and marijuana were three times as likely as nonsmokers to have clinically confirmed COPD (chronic obstructive pulmonary disease); people who smoked only cigarettes had a slightly lower risk.

The study is among the first to suggest a synergistic relationship between marijuana and tobacco use among older people who are most at risk for COPD.

"This effect suggests that smoking marijuana may act as a primer, or sensitizer, in the airways to amplify the adverse effects of tobacco on respiratory health," says study researcher Wan C. Tan, MD, of the University of British Columbia and St. Paul's Hospital in Vancouver, Canada.

COPD Risk

About 12 million Americans are currently living with a diagnosis of COPD; an equal number are believed to have the disease and not know it, according to the National Heart, Lung and Blood Institute.

In the U.S, the term COPD includes both emphysema and chronic bronchitis. With COPD, breathing becomes more difficult over time.

Largely caused by cigarette smoking, COPD is the fourth leading cause of death in the U.S.

While the link between tobacco and COPD is well established, far less is known about the impact of marijuana use on the lungs.

Some studies have found that even short-term heavy marijuana smoking can worsen lung function, while others have not shown this association.

Even less is known about the combined effects of smoking cigarettes and pot, Tan tells WebMD.

The study by Tan and colleagues included 878 residents of Vancouver, Canada participating in a larger investigation examining COPD prevalence.

Participants were considered tobacco smokers if they had smoked at least 365 cigarettes in their lifetime, and were considered marijuana smokers if they reported having ever smoked pot. The researchers defined "substantial" marijuana use as having smoked at least 50 marijuana cigarettes.

The average cigarette smoker in the study had smoked for 16 years, while the self-described pot smokers had smoked an average of 84 marijuana cigarettes.

When COPD was clinically confirmed though a diagnostic method known as spirometric testing:

• The incidence of COPD among participants who smoked cigarettes alone was 2.7 times higher than among nonsmokers.
• The incidence of COPD was 2.9 times higher among participants with a history of smoking both cigarettes and pot, even after controlling for other risk factors for the pulmonary disease.
• COPD risk among people who smoked marijuana, but not tobacco, was slightly higher than among nonsmokers, but the increase was not statistically significant.

The study appears in the April 14 issue of the Canadian Medical Association Journal.

See the article "Marijuana and chronic obstructive lung disease: a population-based study" on page 814.

Over the past 2 decades, studies have addressed the possible relation between smoking marijuana and COPD by systematically assessing respiratory symptoms and measuring lung function in smokers and nonsmokers of marijuana or tobacco.These cross-sectiona ...read more...

Eur Respir J. 2010 Jan;35(1):42-7. Epub 2009 Aug 13.

Effects of cannabis on lung function: a population-based cohort study.

Hancox RJ, Poulton R, Ely M, Welch D, Taylor DR, McLachlan CR, Greene JM, Moffitt TE, Caspi A, Sears MR.

Dunedin Multidisciplinary Health and Development Research Unit, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand. bob.hancox@otago.ac.nz

Comment in:

• Eur Respir J. 2010 Jan;35(1):3-5.

Patients with the severe lung disease COPD (chronic obstructive pulmonary disease) often suffer from appetite loss and cachexia (weight loss) resulting in reduced general well-being and early mortality. In an open clinical study THC improved appetite and well-being and resulted in weight gain.

18 COPD patients aged 49 to 81 years with a mean body weight of 48.5 kg were included in the study under the guidance of Dr. Karl-Christian Bergmann at the Clinic for Allergies and Asthma in Bad Lippspringe, Germany. In the six months before entering the clinic 7 participants had a constant body weight and 11 lost 2.3 kg on average.

They received 3.3-4.2 mg THC two times daily as oily drops delivered by THC Pharm, half an hour before breakfast and dinner. Mean treatment duration was 16 days resulting in a considerable improvement of appetite, general well-being and functional performance (36 per cent mean increase in walking distance) and an average gain in body weight of 1.5 kg, which is much regarding the short treatment period. Side effects were mild.

(Source: Lecture by K-C Bergmann on 17 March 2005 at the Meeting of the German Society of Pulmonology in Berlin)