The per capita rate of daily or near-daily cannabis use skyrocketed 15-fold between 1992 and 2022, according to a 2024 Carnegie Mellon University study. In fact, 40% of the people who report using cannabis in the past month now report using it this frequently.

Regular cannabis use has become even more common than regular alcohol use: In 2022, 17.7 million Americans reported daily or near-daily cannabis use, compared to 14.7 million daily or near-daily drinkers. This was the first time cannabis has overtaken alcohol on this measure.

Cannabis has also become increasingly potent. Samples analyzed averaged under 4% THC in 1995. By 2022, the average had quadrupled to roughly 16%, according to the National Institute on Drug Abuse. Cannabidiol content has fallen over the same period. This matters because CBD blunts some of THC’s psychoactive effects. So today's cannabis isn't just stronger, it's lost some of its built-in buffer.

So where’s the harm? One clear example: cannabis hyperemesis syndrome, a condition where regular users develop cyclical vomiting, often severe enough to come to the ER and sometimes even require hospital admission. CDC counted nearly 200,000 of these ER visits between January 2023 and May 2026.

As a practicing ER physician, I see CHS on a regular basis. Patients present to the ER, often violently ill with vomiting and abdominal pain. They report using cannabis sometimes several times a day, commonly for years. When I tell them cannabis is why they're sick and vomiting, the most common reactions are astonishment and disbelief.

That’s just one example of the harms of regular cannabis use. Here’s what the broader evidence now shows about what happens with regular use, symptoms experienced when people try to quit, the health dangers and what patients and clinicians should actually be doing with all this information.

With regular use, cannabis can be addictive. This runs counter to popular belief. Using PET imaging in chronic daily cannabis smokers, researchers found that cortical CB1 receptors — the receptors THC binds to — were downregulated by roughly 20%. The magnitude of downregulation correlated with the years of use.

This provides a physiologic explanation for two things regular users commonly describe. First, tolerance develops. Second, the anxiety relief that made cannabis appealing tends to erode over months of daily use. The brain adjusts to the drug. And as a result, it needs more of it to get the same effect.

The flip side is that when regular users stop, there’s often an uncomfortable withdrawal. A 2020 meta-analysis covering 23,518 participants in JAMA Network Open found a prevalence of cannabis withdrawal of 47% among people with regular or dependent use.

The syndrome includes irritability, anxiety, disrupted sleep and vivid dreams, appetite loss, restlessness and low mood. Sweating, nausea and sometimes abdominal pain are also common. Symptoms tend to cluster in the first week after cessation.

A systematic review estimated that 22% of people who use cannabis meet criteria for a cannabis use disorder — meaning there is a real dependence on the drug. That risk rises to 33% among young people who use weekly or daily.

Sleep is the single most common reason patients give me for nightly use. And it's also the reason most quit attempts fail. THC shortens the time it takes to fall asleep, but it also suppresses REM sleep. When people stop, the suppressed REM returns all at once as intensely vivid, often unpleasant dreams, sometimes alongside insomnia.

This rebound is a withdrawal phenomenon that usually resolves within one to two weeks. For those interested in quitting, it’s worth knowing that the first week will be the worst and in the second week, sleep usually improves.

The problem is that withdrawal and disrupted sleep can pull people back into daily use, even when they genuinely want to quit.

A 2019 study published in The Lancet Psychiatry compared 901 patients with first-episode psychosis against 1,237 matched controls. Daily cannabis use carried an odds of psychotic disorder of 3.2 compared with never-use. That rose to 4.8 for daily use of a high-potency product (defined as 10% THC or greater).

Another population study in more than 13 million Ontario Residents in JAMA Network Open found that the population-attributable fraction for cannabis use disorder in new schizophrenia diagnoses nearly tripled — from 3.7% before legalization to 10.3% afterward. The highest fraction was in men aged 19 to 24.

For heart attacks and strokes, in a study of 434,104 people, daily cannabis use was linked with a 25% increase in the odds of myocardial infarction and a 42% increase in the odds of a cerebrovascular event, with a graded relationship across days of use per month. Among people who’d never smoked tobacco, the daily-use associations were larger still: 49% for heart attack and 116% for stroke.

When it comes to cognition, the large brain imaging study of its kind examined more than 1,000 young adults aged 22 to 36 across seven thinking tasks. Heavy lifetime use, defined as more than 1,000 exposures to cannabis, was associated with lower brain activation during a working memory task in 63% of users, and activation levels tracked with verbal memory performance and measured intelligence.

What regular cannabis appears to do is blunt the capacity to hold and manipulate information in the moment. This is the capacity that’s most relevant to work, school as well as driving.

Regarding cancer risk, there was older reassuring data that found no elevated risk linking cannabis use and lung cancer, even among heavy smokers. That evidence is now being challenged. A study that tracked roughly 150,000 propensity-matched participants reported a relative risk of lung cancer of 3.9 among adults with cannabis use disorder.

The first thing to know is that frequency of use and potency drive nearly all of the risk. A monthly low-dose edible and a daily concentrate habit are fundamentally different exposures.

Second, if you want to know whether you’re dependent, stop for two weeks and see what happens. Irritability, insomnia and appetite loss in that window suggest some degree of dependence has set in.

Third, cyclic vomiting in a daily user is cannabis until proven otherwise, and the only durable treatment is cessation. Traditional antiemetics to control nausea don’t work well. Topical capsaicin and hot showers sometimes offer temporary relief. Repeat ER visits are common. And in the ER, we commonly use intravenous haldol, a powerful antipsychotic drug, to treat symptoms.

Fourth, the risk-benefit calculation is worst for those under age 25. That’s when the brain is still developing and the psychosis signal is most concentrated in the data.

Ultimately, the United States has commercialized a drug faster than it has characterized its risks. Now, the evidence base is catching up. None of this argues for recriminalization. Instead, it means that people should understand what daily use of high-potency THC products actually does to the body.

It needs to be explained in the same clear terms doctors use for alcohol and tobacco. In my experience, patients are generally willing to hear it. Many have just never been told.