Cigarettes and joints both deliver smoke into your lungs, but the similarities run thinner than most people assume. The two differ in their active chemicals, the way people inhale them, the specific health risks they carry, and even the particle pollution they leave behind in a room. Cannabis smoke contains cannabinoids while tobacco smoke contains nicotine, and that pharmacological split drives a cascade of different effects on your brain, your lungs, your heart, and your cells.
What Is Actually in the Smoke
When plant material burns, it produces thousands of chemical compounds regardless of what plant it is. A comprehensive analysis of mainstream tobacco and marijuana smoke detected roughly 4,350 distinct compounds in tobacco smoke and about 2,575 in marijuana smoke. Of the compounds researchers could identify, 173 in tobacco and 110 in marijuana are known to cause harm through cancer-promoting, mutation-causing, or otherwise toxic mechanisms, with 69 of those toxic compounds shared between the two.
1Scientific Reports. Comprehensive characterization of mainstream marijuana and tobacco smokeSo tobacco smoke carries more harmful compounds overall, but marijuana smoke is far from clean. The reason the cancer outcomes seem to diverge despite chemical overlap comes down to what else is in the smoke. Cannabis smoke contains cannabinoids like THC and CBD, while tobacco smoke contains nicotine. Research examining the biological consequences of inhaling each type of smoke suggests that cannabinoids and nicotine interact with cellular pathways in fundamentally different ways, which may help explain why tobacco smoke has a much stronger established link to lung cancer than cannabis smoke does.
2PubMed Central. Cannabis and tobacco smoke are not equally carcinogenicThat said, the cancer question is not fully settled. A case-control study in New Zealand found that the risk of lung cancer increased about 8% for each joint-year of cannabis smoking (after adjusting for tobacco use), compared to about 7% for each pack-year of cigarette smoking. People in the highest category of cannabis use had a roughly sixfold increase in lung cancer risk compared to nonusers, even after controlling for cigarette smoking.
3European Respiratory Journal. Cannabis use and risk of lung cancer: a case–control studyHow People Inhale Them Differently
If you have ever watched someone smoke a joint versus a cigarette, you have probably noticed the technique is different. Joint smokers take larger puffs, inhale more deeply, and hold the smoke in their lungs longer. Research confirms this pattern: puff volumes are roughly two-thirds larger, inhalation depth is about a third greater, and breath-holding time is around four times longer with marijuana compared to tobacco.
4PubMed. Cannabis: Similarities and differences with tobaccoThese differences in technique have real consequences. A study measuring what happens when people smoke single cigarettes versus single joints found that marijuana smoking produced nearly five times the increase in blood carbon monoxide levels compared to tobacco, roughly three times as much tar inhaled, and about a third more tar retained in the airways. Much of that comes down to the deeper, longer inhalation rather than the plant material itself. Most joints also lack a filter, which means more particulate matter reaches the lungs with each puff.
5PubMed Central. Pulmonary hazards of smoking marijuana as compared with tobaccoThis creates a paradox that confuses a lot of people: per puff, a joint may actually deliver more tar and carbon monoxide than a cigarette. But the average cigarette smoker consumes far more total product over the course of a day and over a lifetime than the average joint smoker. A pack-a-day cigarette habit means roughly 20 cigarettes and 200 or more puffs daily. Even a heavy cannabis user rarely approaches that volume. Total exposure matters as much as per-puff exposure, which is why comparing one joint to one cigarette can be misleading in either direction.
Effects on the Airways and Lungs
Both types of smoke irritate the airways, and the overlap in respiratory symptoms is striking. Marijuana use is associated with chronic cough, phlegm production, wheezing, and chest sounds without a cold, mirroring many of the same symptoms seen in cigarette smokers.
6PubMed Central. Respiratory effects of marijuana and tobacco use in a U.S. sampleChronic bronchitis, which is persistent inflammation of the bronchial tubes, develops in regular smokers of either substance. But the encouraging finding here is that it appears to be reversible. A study tracking people over time found that continuing smokers of either marijuana or tobacco had a significantly higher likelihood of chronic bronchitis compared to never-smokers, but former smokers of either substance were no more likely to have chronic respiratory symptoms than people who had never smoked at all.
7PubMed. Impact of changes in regular use of marijuana and/or tobacco on chronic bronchitisWhen it comes to deeper measures of lung function, the picture gets more surprising. Among tobacco smokers enrolled in a large lung-health study, those who also used marijuana actually showed better lung function on several measures. Current and former marijuana smokers had significantly higher forced expiratory volume (how much air you can blow out in one second) and forced vital capacity (total air you can exhale), and current marijuana users showed less emphysema on imaging, even after adjusting for tobacco use and other factors.
8Journal of Chronic Obstructive Pulmonary Disease. Marijuana Use Associations with Pulmonary Symptoms and Function in Tobacco Smokers Enrolled in the Subpopulations and Intermediate Outcome Measures in COPD Study (SPIROMICS)Researchers are not entirely sure why marijuana users sometimes show preserved or even enhanced lung-function numbers. One theory involves the deep inhalation technique itself stretching the lung tissue, which could inflate capacity measurements without actually meaning the lungs are healthier. Another possibility involves anti-inflammatory effects of cannabinoids. But the picture is not all rosy. A study of COPD patients found that people who smoked both cannabis and tobacco had higher lung volumes than tobacco-only smokers but also significantly more bullous emphysema, where large air pockets form in the lung tissue and can rupture.
9PubMed. Impact of cannabis smoking in patients with COPD: A retrospective cross-sectional study in a safety-net hospitalHeart and Blood Vessel Risks
Tobacco’s devastating effect on the cardiovascular system is one of the most well-established findings in medicine. Cannabis has received far less scrutiny on this front, but the evidence that is emerging gives reason for caution. A large analysis of U.S. adults found that daily cannabis use was associated with about a 25% higher risk of heart attack, a 42% higher risk of stroke, and a 28% higher risk of the combined outcome of coronary heart disease, heart attack, and stroke compared to nonusers, even after adjusting for other risk factors.
10PubMed Central. Association of Cannabis Use With Cardiovascular Outcomes Among US AdultsWhat makes this finding harder to dismiss is that the cardiovascular risk persisted even among people who had never smoked tobacco. Among never-tobacco-smokers, daily cannabis users had roughly 49% higher odds of heart attack and more than double the odds of stroke compared to nonusers. That suggests the cardiovascular effect is not just residual tobacco exposure being mislabeled. The risk also followed a dose-response pattern, meaning fewer days of cannabis use per month carried proportionally lower risk than daily use.
10PubMed Central. Association of Cannabis Use With Cardiovascular Outcomes Among US AdultsThe mechanism likely involves the acute effects of THC on the cardiovascular system: it raises heart rate, can alter blood pressure, and may affect how blood vessels respond. Whether these risks apply equally to non-smoked forms of cannabis is still being studied, but the smoked route adds all the combustion-related vascular damage on top of the drug’s own effects.
What Happens to Your Gums
Tobacco smoking is a well-known destroyer of gum health, so it is natural to ask whether joints do the same. The answer appears to be yes, and possibly independently of tobacco. A long-running study following people from birth to age 32 found that high cannabis exposure was associated with significantly more periodontal attachment loss, which is the separation of gum tissue from the tooth, a hallmark of gum disease. People in the highest cannabis exposure group had about 2.2 times the risk of new attachment loss compared to those who had never used cannabis, even after controlling for tobacco smoking, dental hygiene, and other factors.
11PubMed Central. Cannabis smoking and periodontal disease among young adultsTobacco smoking was also strongly linked to gum disease in that same study, as expected. But there was no interaction between the two, meaning the effects of cannabis did not depend on whether the person also smoked tobacco. Each substance appeared to damage the gums on its own. The likely culprits include the heat of the smoke, immune suppression in the gum tissue, and reduced blood flow, all of which both cigarettes and joints can cause through slightly different pathways.
Epigenetic Aging and Lasting Cellular Marks
One of the more unsettling recent findings involves what smoking does to your DNA’s chemical coating, specifically the methyl groups that sit on top of genes and regulate how they switch on and off. Both tobacco and cannabis smoking leave detectable marks on these patterns, and some of those marks persist even after you quit.
A study comparing cannabis smokers, former cannabis smokers, and never-smokers found widespread disruptions across the genome in both current and former users, with thousands of affected genes shared between the two groups. Many of the disrupted pathways were related to aging and cancer.
12PubMed Central. Cannabis smoking is associated with persistent epigenome-wide disruptions despite smoking cessationWhen researchers looked specifically at epigenetic clocks, which estimate biological age from these DNA patterns, they found that cigarette smoking had a larger impact on epigenetic aging than cannabis smoking. Current cigarette smokers showed a mean epigenetic age acceleration of about 8.9 years compared to never-smokers. Current cannabis smokers showed about 4.2 years of acceleration. Both effects are concerning, but cigarettes aged cells roughly twice as fast by this measure.
13European Respiratory Journal. Cannabis smoking is associated with advanced epigenetic ageA separate cohort study identified nine specific DNA methylation sites that remained altered in long-term cannabis users after accounting for tobacco, alcohol, and other drug use. There were 17 such tobacco-specific sites. One notable finding was that people who had quit cannabis showed less extreme changes at these sites than current users, suggesting some partial reversibility, though not a full return to baseline.
14Molecular Psychiatry. DNA methylation profiles of long-term cannabis users in midlife: a comprehensive evaluation of published cannabis-associated methylation markers in a representative cohortSecondhand Smoke Indoors
If you live with someone who smokes, or you are deciding which substance is “safer” to use indoors, the secondhand exposure data might surprise you. Researchers measured fine particulate matter (PM2.5) in nine rooms of a two-story house after machine-smoking a single tobacco cigarette or a single marijuana joint in the living room. The five-hour average PM2.5 concentration from a tobacco cigarette was about 15 micrograms per cubic meter. The same measurement from a marijuana joint averaged about 66 micrograms per cubic meter, roughly 4.4 times higher.
15PubMed. Measuring PM(2.5) concentrations from secondhand tobacco vs. marijuana smoke in 9 rooms of a detached 2-story houseThat finding likely reflects both the lack of a filter on joints and the denser smoke that marijuana produces. Joints tend to smolder more between puffs, and the sidestream smoke from the burning tip contributes heavily to room-level particulate counts. For context, the World Health Organization recommends that 24-hour average indoor PM2.5 stay below 15 micrograms per cubic meter. A single joint exceeded that threshold for five hours throughout the entire house, not just the room where it was smoked. If you assumed joints were the “cleaner” option for indoor air quality, the data says the opposite.
Mixing the Two Together
In many parts of the world, cannabis and tobacco are not smoked separately. Spliffs, which contain both substances rolled together, and blunts, which use a tobacco leaf wrap around cannabis, are common. This co-use pattern creates a distinct set of risks that neither substance produces alone. A systematic review found that using co-administered marijuana and tobacco products was associated with perceptions of lower risk, greater dependence on both nicotine and marijuana, and stronger subjective effects from the marijuana.
16PubMed. Marijuana and tobacco co-administration in blunts, spliffs, and mulled cigarettes: A systematic literature reviewThe dependence angle is especially important. A longitudinal study of young cannabis users in the UK found that cigarette smoking independently predicted cannabis dependence, even after controlling for how often the person used cannabis. Tobacco use accounted for about 29% of the variation in cannabis dependence severity, and it mediated the relationship between cannabis use frequency and dependence. In plainer terms, adding tobacco to your cannabis habit appears to make the cannabis habit harder to control.
17PubMed Central. Associations between cigarette smoking and cannabis dependence: A longitudinal study of young cannabis users in the United KingdomThere is some evidence of self-awareness among co-users. Research on spliff users found that people who smoked both tobacco and spliffs were less likely to want their first joint within an hour of waking, which researchers interpreted as a form of life-functioning harm reduction. Some participants appeared to recognize that combining the two substances amplified harms and tried to moderate at least one dimension of their use.
18PubMed Central. The Intersection between Spliff Usage, Tobacco Smoking, and Having the First Joint after WakingImpairment Behind the Wheel
Tobacco and cannabis diverge sharply when it comes to acute cognitive and psychomotor effects. Nicotine is a mild stimulant that may slightly improve reaction time and attention in the short term. THC does the opposite. Cannabis smoking increases lane weaving, impairs reaction time, and disrupts divided-attention tasks. Drivers tend to compensate by slowing down, which is a real behavioral difference from alcohol-impaired drivers, who tend to speed up. But the compensation fails as tasks get more complex, like merging, reacting to unexpected obstacles, or navigating unfamiliar roads.
19PubMed Central. Cannabis effects on driving skillsFrequent cannabis smokers sometimes claim tolerance protects them, and there is some truth to this for simple tasks. But experimental data show that even experienced users still show impairment on complex tasks. The impairment window after smoking is typically a few hours, shorter than the period during which THC remains detectable in blood, which matters for interpreting roadside drug tests.
19PubMed Central. Cannabis effects on driving skillsMetals in the Plant Material
Combustible products carry trace metals from the soil, and this applies whether the plant is tobacco or cannabis. A comparison of commercial hemp cigarette fillers against published data on tobacco cigarettes and little cigars found that metal concentrations were broadly similar across the two, with some notable exceptions. All hemp cigarettes had cadmium levels below the lowest reportable limit, significantly lower than tobacco products. But several hemp cigarette brands had chromium, nickel, arsenic, and lead concentrations above some state action limits.
20PubMed Central. Comparison of selected metals in the fillers of 14 commercial hemp cigarette brands to commercial tobacco cigarettesThis is worth knowing because the regulatory infrastructure around tobacco has been developing for decades. Cigarettes are subject to manufacturing standards, labeling requirements, and contaminant monitoring in most countries. Cannabis products, even in legal markets, often face a patchwork of testing requirements that vary by state or country. A cigarette bought in New York and one bought in Texas will be subject to the same federal rules. Two joints bought in different states may have been grown under completely different soil and pesticide standards, and the heavy metal content could vary accordingly. As cannabis legalization expands, this regulatory gap is something consumers should be aware of, especially if they assume that a “natural” product is automatically cleaner than a manufactured one.