We know a fair amount how about how marijuana use affects chronic users, who sometimes see negative cognitive effects from that use — especially if they started when they were young. But researchers want to know more about how marijuana affects what's probably the most common user — the "casual" user who doesn't smoke every day or even every week, but just every so often.
This becomes more and more important as legalization makes marijuana more accessible.
How does marijuana affect kids when they first start using it?
Following kids over a long period of time is probably the best way to understand when and why they start using a substance, but researchers would never just give marijuana to kids and have them start using regularly, as that would be unethical. So for now, we don't know how kids change after they first start using cannabis and other substances.
The ongoing ABCD study should help answer those questions. ABCD is a research effort that will follow 10,000 kids around the country — starting when they are 9 or 10 years old— for 10 years. It's coordinated out of UCSD and there are 21 different sites around the country.
For this study, researchers will analyze the schools kids are enrolled in, examine at where they live, track images of their brains, see how much they exercise and sleep, and more. They'll track everything from stress to puberty hormones to substance use. They'll also see them before and after they begin experimenting with any substances, including marijuana, alcohol, nicotine, and other drugs.
When patients use medical marijuana regularly, how does it affect their life?
Even though we know marijuana can treat conditions like chronic pain, we don't yet know how exactly that consumption will affect patients' sleep, cognitive ability, brain activity, and general quality of life.
An ongoing study at the MIND program in Massachusetts should help answer those questions and more by following a group of medical marijuana users over time (longer than a year) to see how their health changes.
How does marijuana affect older adults?
We have lots of data on young users but little data on older users who might be starting to use for the first time or using again after not doing so for decades. This applies to new recreational users and to many potential medical users. Those older people are probably less susceptible to any of the potential negative brain changes that researchers fear very young users might experience if they start smoking regularly.
In fact, one of the first studies of older medical users from the MIND project had an encouraging finding. Their preliminary results showed that three months into their medical marijuana treatment, a group of patients (24 people, still relatively small) showed significant improvement in tests of cognitive function. Tests of heavy recreational smokers in the past have shown worse cognitive function. This was the opposite, though it can probably be explained by the fact that before treatment, pain could have impaired their cognitive abilities.
The cannabinoids from marijuana tap into that same system, which is why the plant has such wide-ranging effects. Understanding these components and how they interact is going to take a good amount of study.
And what do those components do?
Of those cannabinoids, researchers say we know a good amount about THC, the one we think is mostly responsible for the "high" people get from marijuana. And we're learning more and more about cannabidiol (CBD) which has been linked to many of the medical uses of the plant. But we need learn more about those two — and then we need to learn what all the rest of those cannabinoids do and how to make use of them.
How do different strains of marijuana change health effects?
Even much of what we think we know isn't really backed up with scientific evidence. It's commonly understood that cannabis can be broadly divided into indica and sativa strains, with indica providing more of the mellowing body-high (theoretically better for relaxation) and sativa providing a more energizing, creative high — and then there are hybrids of the two.
But there are no scientific studies that prove this, making it hard for recreational smokers to know exactly what they're getting and what effect it'll have.
Does the increasing 'strength' of pot matter?
You can get stronger pot now than ever before, largely because of innovations in growing practices. Every tweak is going to change the health effects of the plant. High THC plants tend to have low CBD, for example, which could be worrisome for medical users, since many of the medical benefits of cannabis seem linked to CBD.
Some researchers want to know what happens when THC levels hit 50, 60, or 70%, something that's already possible with some concentrated forms of marijuana.
Smoking, vaping, or eating — how much do the methods a person uses to consume marijuana matter?
When it comes to marijuana, "millions of people are using different types of cannabis products for supposedly therapeutic purposes," says Ryan Vandrey, an associate professor of psychiatry who researches marijuana at Johns Hopkins Medicine.
Different, strains, different concentrations, all consumed in different ways. At Johns Hopkins, Vandrey is studying the how different ways of consuming marijuana — orally, smoking, vaping — all affect the body. And while he says that not all of his work can be talked about yet, we do know that the mode of ingestion makes a big difference for how people feel the effects and how they manifest themselves.
At present, that's hard to study. The marijuana researchers can give people for experiments has to come from approved facilities and tends to be far weaker than what people actually use. A researcher in Colorado can walk into a store and buy marijuana, but they can't get approval to give that product to participants in a study.
How should medical cannabis products be tested?
There's no one approved system for testing cannabis products, so people running two different tests on marijuana samples might get different results. Those results might vary even more if they use a test meant for conventional marijuana (flower) on an edible.
it's not clear that a fully accurate means of testing cannabis products exists yet. One analysis of 75 medical marijuana products purchased in Los Angeles, San Francisco, and Seattle found that only 17% were accurately labeled. Some sort of national standard might require devising more accurate tests.
How risky is marijuana use in pregnancy?
It's important to learn how safe marijuana is for pregnant women. There are connections between marijuana use, low birth weight, and time spent in the NICU for infants, so we certainly can't say it's safe, even if some women are already using it to control nausea.
Are there people that are particularly negatively or positively affected by marijuana use?
Many substances affect people differently because of characteristics like age, sex, genetics, or other factors. Medical researchers want to know if some patients may particularly benefit from cannabis use.
At the same time, scientists also want to know if marijuana could be riskier for some users than others. For example, there is some concern that patients already susceptible to schizophrenia may increase their risk of developing the illness by using marijuana.
Are there ways to counteract any of the negative effects of marijuana use?
Even though most researchers think marijuana causes less harm than alcohol or than opioid drugs (both of which can kill users), that doesn't mean cannabis use is risk free. Chronic, heavy users do seem to suffer some negative cognitive effects, especially if they start at a young age.
Researchers want to know if certain behaviors or interventions, like exercise programs, could help counteract those effects.