I help the homeless with addiction. Marijuana has clear negative health effects.

I have served in addiction medicine with the homeless for over 30 years. Contrary to what you may hear from some big law firms, legalizing marijuana in Florida (or anywhere else) is not a good thing.

I fully believe it is a gateway drug with significant negative effects on one’s mental and physical health.

Below are just a few of the concerns cited in the medical literature that demonstrate to me why this drug should not be legalized.

Daily cannabis use over several years can increase the risk of head and neck cancer by up to five times, according to new research that analyzed more than 4 million medical records.

The study, published Aug. 8 in the Journal of the American Medical Association-Otolaryngology-Head & Neck Surgery, shows that people with cannabis-related disorders have a higher risk of oral, oropharyngeal, and laryngeal cancer compared with those who do not have these disorders.

Individuals who visited the ER for substance-induced psychosis had a 160% increased risk of developing a schizophrenia spectrum disorder compared to the general population, according to a large retrospective cohort study based in Ontario, Canada.

Three years later, 18.5% of people with substance-induced psychosis were diagnosed with a schizophrenia spectrum disorder. Cannabis-induced psychosis carried the greatest risk, particularly for the male sex in younger versus older individuals.

It is becoming increasingly clear that the adolescent brain is particularly vulnerable to cannabis. This puts teenagers at risk of impaired brain development, mental health problems (including psychosis) and cannabis use disorders.

The legalization of marijuana in a growing number of US states may also exacerbate the problem of exposure to toxic metals. A 2023 study found that cannabis users had significantly higher levels of lead and cadmium in their blood and urine than non-users. These elevated levels are associated with impaired cognitive function and cognitive impairment.

Teens who use cannabis recreationally are 2 to 3 times more likely to experience depression and suicidal thoughts than non-users.

Lyrics: I had high hopes for Trump in 2016. It didn’t take me long to realize my mistake.

Marijuana can cause a lung disease called pulmonary arterial hypertension. Smoking cannabis can damage lung tissue and cause scarring and damage to small blood vessels.

Cannabis, like alcohol, negatively affects several skills necessary for safe driving.

Cannabis can make the heart beat faster and can raise blood pressure immediately after use. It could also increase the risk of stroke, heart disease and other vascular diseases.

These are just a few of the reasons to vote NO on Amendment 3.

Karen McCarthy, MD, volunteer medical director, City Rescue Mission Clinic, Jacksonville

This guest column is the opinion of the author and does not necessarily represent the views of the Times-Union. We welcome diversity of opinion.

This article originally appeared in the Florida Times-Union: Marijuana health risks are a good reason to vote NO on Amendment 3