Long-term cannabis use affects lung function but not like tobacco.

A long-term study involv­ing just over a thou­sand par­tic­i­pants found that smok­ing cannabis reg­u­lar­ly can alter the func­tion of your lungs as you age. Unlike smok­ing a cig­a­rette, how­ev­er, cannabis appears to have a slight­ly dif­fer­ent impact on a per­son­’s breathing.

As an adult, smok­ing is asso­ci­at­ed with a grad­ual decrease in the amount of air you can expel from your lungs in a giv­en amount of time. In com­par­i­son, smok­ing cannabis in the cur­rent study was linked to high­er total lung volumes.

Ulti­mate­ly, the authors found that both changes led to sim­i­lar end results – air­way con­stric­tion and hyper­in­fla­tion and gas trapping.

These lung func­tion pat­terns match pre­vi­ous results from the same cohort, which were col­lect­ed 13 years ear­li­er when the par­tic­i­pants were 32 years old.

“Although the effects of cannabis were adverse, the pat­tern of changes in lung func­tion was not the same,” says res­pi­ra­to­ry spe­cial­ist Bob Han­cox from the Uni­ver­si­ty of Ota­go in New Zealand.

“Research has found that pro­longed cannabis use leads to exces­sive swelling of the lungs and increas­es resis­tance to air­flow to a greater extent than tobacco.”

To date, there is lit­tle research on the lung effects of cannabis use. Some stud­ies sug­gest that smok­ing cannabis flower can lead to acute bron­chi­tis-like symp­toms, while oth­er stud­ies sug­gest that even after sev­en years of smok­ing, lung func­tion is not sig­nif­i­cant­ly impaired.

One of the main chal­lenges is to dis­tin­guish the effects of cannabis from tobac­co, since most cannabis users are also tobac­co smokers.

Par­tic­i­pants includ­ed in the cur­rent New Zealand study were no excep­tion. Most were tobac­co and cannabis smok­ers, but even among those who had nev­er smoked tobac­co before, the authors found sim­i­lar pat­terns in lung function.

Although it is easy to mea­sure the num­ber of cig­a­rettes a per­son smokes per day, there is cur­rent­ly no stan­dard­ized form of joint. As such, the cur­rent study could only dif­fer­en­ti­ate between dai­ly cannabis smok­ers and those who smoke less than once a week.

This like­ly under­es­ti­mates the amount of cannabis some par­tic­i­pants are con­sum­ing, mak­ing it dif­fi­cult to tell how much you need to smoke to put your lung health at risk.

The heav­i­est cannabis users in the study tend­ed to also be tobac­co smok­ers, fur­ther com­pli­cat­ing the results.

“Cannabis users tend to smoke sig­nif­i­cant­ly few­er times per day than tobac­co smok­ers and it is pos­si­ble that par­tic­i­pants did not smoke enough cannabis to have a mea­sur­able effect on some aspect of lung func­tion” , note the authors.

“How­ev­er, this seems unlike­ly giv­en the strong asso­ci­a­tions with high­er lung vol­umes and low­er air­way conductance.”

These asso­ci­a­tions were par­tic­u­lar­ly strong and con­sis­tent among those who smoked both tobac­co and cannabis. In fact, these par­tic­i­pants showed a slight ten­den­cy to reduce gas trans­fer, mean­ing their lungs weren’t as effi­cient at exchang­ing oxy­gen for car­bon dioxide.

The authors are con­cerned that this puts some peo­ple at risk for emphy­se­ma, although it is still unclear what these changes in lung func­tion do to a per­son­’s over­all lung health.

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