Most people assume they already know the answer to an age-old debate about substances. Alcohol has earned a notorious reputation over decades of research linking it to liver disease, cancer, and countless preventable deaths. Meanwhile, marijuana has enjoyed a cultural rehabilitation in recent years, with 24 states legalizing recreational use and advocates touting its medical benefits. A whopping 17 percent of Americans admitted to smoking a joint at some point during 2023, and many view cannabis as a relatively harmless way to unwind.
World Health Organization officials have declared there is no safe level of alcohol consumption, labeling it a “toxic, psychoactive and dependence-producing substance.” Booze can cause at least seven types of cancer, including bowel cancer and breast cancer in women. With such damning evidence against alcohol, you might assume the verdict is obvious.
But a brain doctor has examined thousands of brain scans to answer the question definitively, and his findings challenge popular assumptions about which substance does more damage to your gray matter. Dr. Daniel Amen, a psychiatrist who founded Amen Clinics, set out to investigate what actually happens inside the brain when people use these substances long-term, and the results might make you reconsider everything you thought you knew.
Inside a Massive Brain Scan Study
Amen Clinics partnered with researchers from Google, Johns Hopkins University, UCLA, and UC San Francisco to conduct one of the largest brain imaging studies ever attempted. Scientists evaluated 62,454 brain SPECT scans from more than 30,000 individuals ranging from 9 months old to 105 years of age.
SPECT imaging, which stands for single photon emission computed tomography, measures regional cerebral blood flow in the brain. Reduced blood flow in certain regions indicates various disorders and can predict how quickly someone’s brain is aging compared to their actual chronological age. Researchers examined 128 brain regions to determine each patient’s predicted brain age, then compared it against their real age to measure accelerated aging.
Patients in the study presented with many different psychiatric conditions, including bipolar disorder, schizophrenia, and attention-deficit hyperactivity disorder. By analyzing such a massive dataset, scientists could isolate specific factors that speed up brain aging and determine which substances and conditions cause the most damage over time.
How Cannabis Ages Your Brain Faster Than Alcohol
Here is where the data defied expectations. Cannabis abuse accelerated brain aging by an average of 2.8 years, while alcohol abuse accelerated it by only 0.6 years. Put another way, regular marijuana users showed brain scans that looked nearly three years older than their actual age, while heavy drinkers showed less than a year of premature aging on average.
For comparison, schizophrenia showed the highest rate of accelerated aging at 4 years, followed by cannabis abuse at 2.8 years, bipolar disorder at 1.6 years, and ADHD at 1.4 years. Interestingly, researchers did not observe accelerated aging in patients with depression, which they hypothesize may result from different brain patterns associated with that condition.
Dr. Amen commented on these findings directly. “Based on one of the largest brain imaging studies ever done, we can now track common disorders and behaviors that prematurely age the brain. Better treatment of these disorders can slow or even halt the process of brain aging. The cannabis abuse finding was especially important, as our culture is starting to see marijuana as an innocuous substance. This study should give us pause about it.”
George Perry, Chief Scientist at the Brain Health Consortium from the University of Texas at San Antonio, called this research essential for understanding how to maintain brain health during aging, noting that studying both modifiable and non-modifiable factors will guide future recommendations for preserving cognitive function.
Cannabis Hyperemesis Syndrome Is Sending Heavy Users to Emergency Rooms
Brain aging is not the only concern emerging from cannabis research. Emergency departments across the country have treated increasing numbers of patients arriving with severe abdominal pain and prolonged vomiting episodes, and these patients share one common trait. Nearly all of them are chronic cannabis users suffering from a condition called cannabis hyperemesis syndrome, or CHS.
CHS triggers cycles of nausea, vomiting, and intense abdominal discomfort that can persist for days at a time. Chronic users may experience these debilitating episodes three to four times per year, with symptoms typically appearing within 24 hours of their most recent use. One study found that 32.9 percent of self-reported frequent marijuana users who visited an emergency department met the criteria for CHS, suggesting the condition may be far more common than previously recognized.
People with CHS often discover that hot baths and showers temporarily relieve their symptoms, leading many to compulsively bathe for hours every day during episodes. Some patients experience such intense pain while vomiting that they scream simultaneously, a phenomenon that emergency room staff have dubbed “scromiting.”
CHS typically develops after about 10 to 12 years of regular cannabis use, though it tends to affect people who consume marijuana at least once weekly and started using during adolescence. Scientists believe the condition results from long-term overstimulation of cannabinoid receptors in the endocannabinoid system, which eventually disrupts the body’s natural control of nausea and vomiting.
Symptoms progress through three distinct phases. During the prodromal phase, which can last months or years, users experience morning nausea and abdominal pain without actually vomiting. Next comes the hyperemetic phase, lasting 24 to 48 hours, when overwhelming nausea and recurrent vomiting take hold. Recovery only begins once a person stops using cannabis entirely, with symptoms gradually disappearing over days or months.
Why Alcohol Still Causes More Real-World Harm
Despite the brain scan findings, Dr. Amen was careful to acknowledge that alcohol remains deeply problematic from a public health perspective. “Now those of you who follow me know neither one are good for you. And quite frankly there are more deaths every year from alcohol than there are marijuana. There’s more domestic violence, there’s more drunk driving accidents, there’s more bad decisions, people ending up in jail.”
At least 60 percent of the American population drinks alcohol, making it far more prevalent than marijuana use. Beyond the seven types of cancer linked to drinking, alcohol contributes to motor vehicle fatalities, domestic abuse, and a wide range of impaired decision-making that lands people in hospitals, courtrooms, and correctional facilities.
So while cannabis may age the brain faster according to SPECT imaging data, alcohol causes more immediate and visible destruction in communities and families. Both substances carry serious risks, and viewing either as “safe” or “harmless” contradicts the available scientific evidence.
Medical Marijuana Has FDA-Approved Applications
Despite concerns about recreational use, cannabis does have legitimate medical applications that distinguish it from alcohol. Medical marijuana programs exist in numerous states to help patients manage specific symptoms, though healthcare providers certify its use rather than prescribing it directly since marijuana remains a Schedule I substance federally.
Approved medical uses include chronic pain relief (particularly neuropathic pain), nausea relief for chemotherapy patients, management of multiple sclerosis symptoms like spasticity, and appetite stimulation for people with HIV or AIDS. Some evidence suggests medical cannabis may help decrease opioid use for pain management, though researchers continue studying these applications.
The FDA has approved several purified substances derived from marijuana. Epidiolex treats seizures in patients with rare forms of epilepsy like Lennox-Gastaut syndrome and Dravet syndrome. Marinol and Cesamet help prevent and treat chemotherapy-related nausea and vomiting, with Marinol also approved for appetite and weight loss issues in HIV and AIDS patients.
Not all healthcare systems certify medical marijuana even in states where it is legal, primarily due to insufficient research and clinical trials on long-term medical applications.
What Heavy Users Should Know About Long-Term Brain Effects
Beyond accelerated aging and CHS, cannabis use carries additional risks that researchers are still working to understand fully. Using marijuana during adolescence or young adulthood, before the brain finishes developing, may affect how the brain builds connections for attention, memory, and learning. Scientists believe these effects may last a long time or even become permanent.
Smoking cannabis products damages lung tissue, increases bronchitis risk, and scars small blood vessels. Marijuana smoking may also increase the risk of stroke, heart disease, and other vascular diseases, while vaping THC-containing products has been linked to lung injury and death.
Frequent marijuana use correlates with higher rates of schizophrenia and other psychoses in people who are already predisposed to these conditions. Long-term use is also associated with periodontal disease, impaired sperm development affecting fertility, and more frequent pain crises in people with sickle cell disease.
Cannabis affects each person differently based on genetics, age, sex, consumption method, and frequency of use. Someone smoking high-potency marijuana regularly faces different risks than someone using low-dose edibles occasionally, and the effects that one person experiences may differ entirely from another person’s reaction.
Quitting Remains Your Only Option for CHS Recovery
For people already suffering from cannabis hyperemesis syndrome, medical professionals offer only one proven cure. Stopping cannabis use completely is the only way to permanently eliminate CHS symptoms. Hot baths may provide temporary relief, but they can actually worsen dehydration from excessive sweating and do nothing to address the underlying condition.
Most people with CHS who quit using cannabis experience symptom relief within 10 days, though full recovery may take several months. During the transition period, healthcare providers may recommend antihistamines like diphenhydramine, capsaicin cream for pain relief, over-the-counter pain relievers, or prescription medications, including benzodiazepines and antipsychotics.
Untreated CHS can lead to serious complications, including severe dehydration, electrolyte imbalances, malnutrition, tooth decay, and injuries to the esophagus. Anyone experiencing dark urine, dizziness, rapid heartbeat, fainting, or sudden confusion should seek emergency medical care immediately, as these symptoms indicate dangerous dehydration levels.
Quitting marijuana can prove difficult for long-term users, with approximately 1 in 10 adult users developing cannabis use disorder. Adolescents face even higher risks, being four to seven times more likely than adults to develop dependence. Anyone struggling to quit can call the Substance Abuse and Mental Health Services Administration helpline at 1-800-662-4357 for free, confidential support available around the clock in English and Spanish.
