Why smoking marijuana is not harmless as many think – 09/01/2023 – Equilibrium

While tobacco use is decreasing among adults in the United States, cannabis use is on the rise.

Laws and policies regulating tobacco and cannabis use are also moving in different directions.

Tobacco policies are becoming more restrictive, with bans on smoking in public places and limits on sales, such as state bans on flavored products.

In contrast, more states are legalizing cannabis for medical or recreational use, and there are efforts to allow cannabis exceptions in smoking laws.

These changes mean that an increasing number of people are likely to be exposed to cannabis smoke. But how safe is direct, passive cannabis smoke?

I am a primary care physician and researcher in a state where cannabis is now legal for both medical and recreational use.

My colleagues and I were interested in how opinions about the safety of tobacco smoke and cannabis have changed during this period of increasing use and commercialization of cannabis.

In our survey of more than 5,000 US adults in 2017, 2020 and 2021, we found that people are increasingly believing that exposure to cannabis smoke is safer than tobacco.

In 2017, 26% of people thought it was safer to smoke a cannabis joint than a cigarette on a daily basis. In 2021, over 44% chose cannabis as their safest option.

People were also more likely to rate secondhand cannabis smoke as “completely safe” compared to tobacco, even for vulnerable groups such as children and pregnant women.

Despite these opinions, recent research raises concerns about the health effects of exposure to cannabis smoke.

Opinions and science

Decades of research and hundreds of studies have linked tobacco smoke to multiple types of cancer and cardiovascular disease.

However, there are far fewer studies on the long-term effects of cannabis smoke. Since cannabis is still illegal at the federal level, it is more difficult for scientists to study it.

It has been particularly difficult to study health outcomes that can take a long time and greater exposure to develop.

Recent reviews of research on cannabis and cancer or cardiovascular disease found these studies to be inadequate because they included relatively few people with heavy exposure, did not follow people long enough, or did not adequately account for smoking.

Many advocates point to the lack of clear findings on the negative effects of exposure to cannabis smoke as proof of its harmlessness.

However, my colleagues and I believe that this is an example of the famous scientific quote that “absence of evidence is not evidence of absence”.

Scientists have identified hundreds of chemicals in both cannabis and tobacco smoke, many of which are carcinogenic and toxic.

Combustion of tobacco and cannabis, whether through smoking or herbal vaporizers, also releases particles that can be inhaled deep into the lungs and cause tissue damage.

Animal studies of the effects of secondhand tobacco and cannabis smoke show similar troubling effects on the cardiovascular system, including impaired blood vessel dilation, increased blood pressure, and reduced heart function.

While more research is needed to determine the risk of lung cancer, heart attacks and strokes caused by cannabis smoke, what is known has raised concerns among public health agencies.

Why do opinions about cannabis matter?

How people perceive the safety of cannabis has important implications for its use and public policy.

Research shows that when people believe something is less risky, they tend to use it more.

Opinions about cannabis safety will also shape medical and recreational cannabis laws and other policies, such as whether cannabis smoke will be treated like tobacco smoke or whether exceptions will be made to smoke-free laws.

Part of the complexity in decisions about cannabis use lies in the fact that, unlike tobacco, clinical trials have shown that cannabis can have benefits in certain contexts.

This includes managing specific types of chronic pain, reducing nausea and vomiting associated with chemotherapy, and increasing appetite and weight gain in people with HIV/AIDS.

It is worth noting that many of these studies were not based on smoked or vaped cannabis.

Unfortunately, while an internet search on cannabis returns thousands of results about the health benefits of cannabis, many of these claims are not backed up by scientific research.

I urge people who want to learn more about the potential benefits and risks of cannabis to talk to health professionals or seek out sources that present an unbiased view of the scientific evidence.

O National Center for Complementary and Integrative Health provides a good overview of studies on cannabis for the treatment of various medical conditions, as well as information about potential risks.

This text was published here

Beth Cohen is Professor of Medicine at the University of California, San Francisco