Regular smokers of marijuana may be putting themselves at increased risk for emphysema, according to a new study conducted in Scotland.
Researchers led by Dr. Martin Johnson of the department of respiratory medicine at Glasgow Royal Infirmary, looked at cases of early stages of emphysema in four men ages 27, 35, 44 and 46 who regularly smoked cannabis.
Results showed that large areas of the men's lungs had disappeared and been replaced with cysts. This is an indication of a form of emphysema typically associated with cigarette smoking, in which the surface area of the lungs is gradually reduced.
All of the subjects had been--or continue to be-heavy users of cannabis. The 27-year-old participant smoked several pipes of pot per day for a number of years. Both men in their 40s smoked two or three joints a day and the 35-year-old had smoked two joints a week for about 20 years.
While the authors report that cannabis is often perceived as harmless, this is not the case. Other than the mind-altering effects of pot, the effects of smoke from cigarettes and cannabis are similar. While pot smokers typically smoke less, they tend to hold in smoke longer.
The physical effects on the lungs of smoking three to four joints a day are equivalent to those produced by smoking a pack of cigarettes a day, said the authors.
Johnson and his team reported that there were fundamental differences between smoking marijuana and tobacco. "A draw on a marijuana 'joint' involves on average a volume two thirds larger, a depth of inspiration a third greater, and a breath holding time four times longer than a draw on a cigarette," they reported.
"When this smoking practice is combined with the lack of filter tips on marijuana cigarettes, it leads to a fourfold greater delivery of tar and a five times greater increase in carboxyhemoglobin per cigarette smoked," the researchers added.
The authors expressed hope that given the growing political pressure to legalize marijuana and other associated substances, their findings would "stimulate further study into their potential lung toxicity."
Jag Khalsa, of the center on AIDS and other medical
consequences of drug abuse (www.drugabuse.gov) at the National Institute of Drug Abuse in Bethesda, Md., said he was encouraged to see further documentation of the harmful effects of pot smoking, adding that these results, in part, confirm what has been previously seen in the field.
Contrary to some popular perceptions, Khalsa said using marijuana is certainly not "harmless." Among the serious consequences of pot smoking are cognitive impairment, short-term memory loss, harmful effects on lungs and a possible association with cancer.
In fact, said Khalsa, current studies are under way looking at possible links between pot smoking and cancer.
Khalsa said he hoped such findings would lead to more research with a greater number of subjects. Marijuana smoking, he concluded, "can cause serious lung injury."
