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Heavy Long-Term Marijuana Use Does Not Impair Lung Function, Says New Study

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.