Smoking pot vs. tobacco: What science says about lighting up

Some researchers are concerned with how legalizing marijuana could change successes in curbing cigarette smoking.

While cigarette smoking is the top risk factor for lung cancer, some of scientific evidence suggests there's no link between marijuana smoking and lung cancer. But there's strong evidence linking long-term cannabis smoking to worse coughs and more frequent bouts of chronic bronchitis.

By Jennifer Peltz

(AP) As more states make it legal to smoke marijuana, some government officials, researchers and others worry what that might mean for one of the country's biggest public health successes: curbing cigarette smoking.

Though there are notable differences in health research findings on tobacco and marijuana, the juxtaposition strikes some as jarring after generations of Americans have gotten the message that smoking endangers their health.

Marijuana advocates say there's no comparison between joints and tobacco cigarettes. A sweeping federal assessment of marijuana research found the lung-health risks of smoking weed appear “relatively small" and “far lower than those of smoking tobacco," the top cause of preventable death in the U.S.

Unlike for cigarettes, there's evidence of certain health benefits from marijuana, such as easing chronic pain. And marijuana can be used without smoking it. Most states now have legal medical pot programs; 10 states and the District of Columbia have approved recreational use.

“They're different products, and they need to be treated differently," says Mason Tvert, a spokesman for the pro-legalization Marijuana Policy Project.

At the same time, studies have shown crossover between marijuana and tobacco use. And while smoking cannabis may be less dangerous than tobacco to lung health, pot doesn't get an entirely clean slate.

Some health officials and anti-smoking activists also worry about inserting legal marijuana into the growing world of vaping, given uncertainties about the smoking alternative's long-term effects.

Here's a look at the issues, science and perspectives:

Smoking pot vs. tobacco

While cigarette smoking is the top risk factor for lung cancer, some of scientific evidence suggests there's no link between marijuana smoking and lung cancer. That's according to a 2017 federal report that rounded up nearly two decades of studies on marijuana, research that's been limited by the federal government's classification of marijuana as a controlled substance like heroin.

While cigarette smoking is a major cause of heart disease, the report concluded it's unclear whether marijuana use is associated with heart attacks or strokes.

But there's strong evidence linking long-term cannabis smoking to worse coughs and more frequent bouts of chronic bronchitis, according to the report from the National Academies of Sciences, Engineering and Medicine.

The report also looked at other effects, finding a mix of possible risks, upsides and unknowns. For example, the report said marijuana can ease chemotherapy-related nausea and adults' chronic pain but also found evidence the drug is linked to developing schizophrenia and getting in traffic crashes.

Tobacco and marijuana use can also go together. Blunts — marijuana in a cigar wrapper that includes tobacco leaves — have gained popularity. And studies have found more cigarette smokers have used pot, and the other way around, compared to nonsmokers.

“One substance reinforces the use of the other, and vice versa, which can escalate a path to addiction," says Dr. Sterling McPherson, a Washington State University medical professor studying marijuana and tobacco use among teens.

The National Academies report found pot use likely increases the risk of dependence on other substances, including tobacco.

So what about vaping?

Vaping — heating a solution into a vapor and inhaling it — has been pitched as a safer alternative to smoking.

Experts have said vaping pot is probably less harmful to the lungs than smoking it, though there's little research on the health effects over time, and they worry about its potency when vaped.

The American Lung Association is concerned that vaping will ultimately prove damaging to lung health and is alarmed about a surge in underage e-cigarette use. And adding legal marijuana to the picture “only makes it a more complicated issue," says Erika Sward, an assistant vice president.

Others, though, think policymakers should view vaping as a relatively safe way to use pot.

Rebecca Haffajee is a University of Michigan health policy professor who co-wrote a 2017 piece calling for recreational marijuana programs to allow only nonsmokable forms of the drug.

“I would say the risks are going to be less with that form of consumption," she said.