How Monthly, Weekly & Daily Marijuana Use Affects You Differently

What are you doing to your body when you pick up a joint or a bong? And what happens the more often you do it? Science has answers, but they're often more complicated than just "things get worse the more you do it". Cannabis, as it turns out, is a complex plant, and has many different kinds of interaction with the human body; and studies into marijuana's impacts over long periods of time are still being done. Plus, there's the problem that many studies seem to contradict each other. So what do we really know about how often you partake and what it does to your health?

Marijuana gets a big portion of press attention when any scientific evidence is found for its benefits or damage, in part because it's insanely popular. It's estimated that 22 million people in America used marijuana in the past month, but that includes a huge range of doses, frequencies, and methods, from the teens lighting up after school to people getting medical marijuana in various legalized states. And on 4/20, the day when you're most likely to get a contact high from smoke by simply walking down the street in a college town, it's important to know what exactly this much-loved plant can actually do to your body depending on how often you use it.

Bustle spoke to Professor of Psychology Mitchell Earleywine of the University of Albany, NY, a world expert on the health impacts of marijuana use, and he pointed out that frequency itself might not actually be one of the big issues. "Work from my lab and others does suggest that frequency of use correlates positively with cannabis-related problems," he said, "but the effect isn't particularly big." So be aware that other issues, like co-using alcohol and the time of life when you started to use weed, may be a big factor for problems, too.

Occasional Use

The interesting thing about marijuana, as a drug, is that it seems to have many different effects on the human system, and we're still trying to figure out how many of those are temporary, what's long-term, and how much dosage is required for certain impacts to be more likely. (And then there's the fact that men react differently to women when it comes to cannabinoids, which is often not used as a factor in studies of weed health impacts.) But a dose every now and then seems mostly safe. "Occasional use by adults is generally safe," Professor Earleywine tells Bustle, "particularly for those who use the vaporizer (a gizmo that heats the plant without igniting it, causing cannabinoids to release in a fine mist that does not carry respiratory irritants so commonly found in smoke)."

One way a smoking session every few months may hurt your body is in immune response. Studies have found that one of the body's more interesting and immediate reactions to weed is in its protection against disease; a study in 2010 looked at cannabinoids, the active compounds in weed, and how the immune systems of rats reacted when they were given a dose. It turned out that a cannabinoid "hit" caused the rats to produce a unique kind of immune cell that actually suppresses the immune system. And there's evidence that cannabinoids interfere elsewhere in our resistance to infection too, from our T-cell count to reactions to things like herpes. (The cancer news isn't all bad; the National Cancer Institute documents studies that show cannabinoids may help with fighting certain tumors, though there's not enough evidence to provide a big headline on that one.)

Otherwise, a single hit will significantly impair your balance, your reaction time, and your ability to form new memories, but these effects will wear off afterwards if you don't keep hitting the bong the rest of the day. This is why, according to the National Institute On Drug Abuse, it's absolutely crucial to avoid driving or operating machinery when you're high, because you're at a much higher risk of crashing or reacting slowly. A study from the University of Oxford has also demonstrated, through injecting subjects with the active ingredients of cannabis, that just one hit can cause an immediate hit of serious paranoia for some users, though it's not clear whether that recurs.

Monthly Use

Determining whether risks increase with dosage when it comes to cannabis is a bit tricky. (For one, people might lie to scientists about how much they actually toke.) But monthly use appears to be linked to temporary harm to cognitive skills like memory, assimilation of new information, and attention. At the moment, according to studies accumulated by Melanie Pinola for Lifehacker, science believes that a monthly user will "spring back" from this damage in their next period of abstinence over the month. We're not sure precisely how long these effects last, as everybody reacts different to weed, though they're most potent in the first few hours after a toke's taken.

One study did look specifically at monthly users, and the health impacts it observed over the longer term weren't actually terrifying. Published in 2014, the study had looked at boys throughout their lives, from 7th grade to age 35. (Again, note that they only looked at boys, so women should take this result with a pinch of salt.) Monthly use was common, and it didn't seem to make a difference to the 35-year-old's current health issues, medications, injuries, or hospitalizations; men who didn't smoke weed had the same outcomes.

Weekly Use

When marijuana usage is on the weekly level, the health risks seem to increase. Interestingly, though, one of the main health side affects appears to be social: weekly marijuana users are more likely than monthly or occasional ones to have friends who use heroin, and are also more likely to be cocaine users. Weekly weed-hits are seen as a kind of a "gateway" for other possible drug use.

The range of health problems associated with weekly use is pretty diverse. One that stands out is the risk of "man boobs," or gynecomastia. Medical Daily reported in 2013 that, after a doctor made the link between weekly use and man-boobs on CNN, the scientific community came out to support him; we're not entirely sure why (the answer likely likes with the interaction of THC, the most potent ingredient in weed, with testosterone levels), but the relationship certainly seems probable.

A 2002 study on cognitive performance, which measured everything from reaction time to memory and dexterity, found that if weekly users went cold turkey for a month, they regained their cognitive powers. Some of us will recover faster than others, but it's still a cause for thought.

And a 2001 study found that weekly smokers were 2.5 times more likely to have a heart attack than those who never did. And, alarmingly, the study found that the most dangerous hours are within the first few hours of partaking, when people are 4.8 times more likely to have a cardiovascular event than normal. Live Science's investigation of the issue indicates that reports of rare cannabis-related heart events go back to the 1960s, but that we're still trying to understand what's going on. (It seems to be something to do with fluctuations in blood pressure and stress on the heart.)

Daily Use

When it comes to daily usage and harm to your lungs, there's actually quite a lot of scientific argument. A 2015 study stated fairly definitively that, even after 20 years of daily use, weed smokers were still able to expel the same amount of air from their lungs as non-smokers, indicating that there had been no damage to their function from getting high. (Interestingly, the scientists involved believed that any increase in chronic coughing was due to the papers used to roll joints, not the weed itself.) But the medical establishment is still warning of potential damage to lungs; the American Lung Association warns of irritation to the cell lining of the airways.

And when the subject is lung cancer, the scientific consensus is also not clear. Cancer Research UK has compared the research available and found that some studies believe there is a link, while others don't believe the indications are strong enough. They point out that the huge variation in the strength of weed, the fact that people sometimes smoke it with tobacco, and the different ways individuals process it all make it quite hard to study for a cancer link. "Although cannabis does increase symptoms of bronchitis like coughing and wheezing, it does not appear to elevate risk for lung cancer," Professor Earleywine says.

The real health impacts of daily use, though, seem to be cognitive. The potential link to schizophrenic symptoms among people who've not previously had any signs is worrying, but there's also an argument that daily, heavy spliff use may actually alter the structure of your brain. A 2014 study found that daily users seemed to have a smaller orbitofrontal cortex, the part of the brain that helps with emotional and decision-oriented processing, but also to have denser links between parts of the brain, possibly to compensate. But a 2015 study found no change in the density of any brain parts in daily marijuana users, so the fact is that we're not entirely sure what's going on.

The Bottom Line

"The data on cannabis and altered brain structure only seem to appear in those who used the plant heavily while still very young," Professor Earleywine cautions. "These findings have failed to replicate in a few publications, and there's a tendency for any failure to replicate to not get much press." He also points out, "As my colleagues often emphasize, the impact of binge drinking on brain structure is dramatically larger."

When it comes to just rating frequency as the determining factor, though, Professor Earleywine points out that there are problems. "Plenty of daily users have literally no problems related to the plant, and some occasional users consume in unsafe ways," he tells Bustle. "[His research team has] a new paper coming out that suggests that daily users who don't experience problems rarely use early in the day, for example." And he identifies another complicating factor: the age you start smoking. "Those who begin use early in life tend to show more problems with the plant than those who start when they are older."

So frequency may not be the be-all and end-all for determining what possible risks you're letting yourself in for; what time of day you smoke, how you do it, and how young you were when you began smoking are all factors, too. The main consensus? You can't generalize too much about frequency, but science has some interesting findings to offer nonetheless.

Images: Giphy, Columbia Records