Over 40 percent people who use medical marijuana quit taking at least one prescription altogether once they have their cannabis card, a new study reveals.

Medical marijuana legalization has swept the US in the last decade, and its relatively sudden acceptance in many states has left some confusion in its wake for consumers, their doctor, regulators and public health officials.

Depending on the state, marijuana is approved to treat conditions like pain, nausea and depression, but for many conditions doctors intend it to be a complement to other medications - not a replacement.

Yet respondents to a University of Michigan survey admitted they often quit other prescriptions once they have marijuana and many don't even tell their primary care doctors.

Over 40 percent of American medical marijuana patients quit another pharmaceutical altogether after getting their cannabis prescription, a new study reveals

An estimated 2.1 million Americans use medical marijuana prescribed to them by a doctor.

But they don't always get that prescription from their primary care provider.

In fact, about a third of them hide their use from their primary care doctors entirely, the new study found.

It may be that - though legally the status of marijuana has changed - users are still wary that their doctors may judge their marijuana use.

Most of the approximately 400 people that answered the University of Michigan survey said that they had used marijuana recreationally in the past, so the shift to the substance being legitimized might a sticking point.

Marijuana was long-considered a gateway drug and even a public health threat, with campaigns like DARE (drug abuse resistance education) targeting the substance.

Now it is thought to have many potential benefits, but isn't treated that way by the federal government or public health officials.

'Public health is still operating in the era of prohibition' by leaving marijuana a Schedule 1 drug, says Dr Daniel Kruger, a public health professor at University of Michigan and lead author of the study.

It still treats cannabis use like 'an abstinence-based program, like sex, and we know that doesn't work,' he adds.

'It's not wild to say "here's this plant that people have used medicinally for 5,000 years" ... why are we not taking it seriously?'

And many patients actually trust this plant more than prescription drugs.

All of the respondents to the new survey showed a preference for medical marijuana over pharmaceuticals - particularly opioids - due in part to its mild or absent side effects.

In some respects, that's good news, particularly amid the opioid crisis, and public health research bears that out. In states like Colorado, where marijuana is now legal for both medicinal and recreational use, opioid prescriptions and overdoses have declined.

According to the new survey, 38 percent of medical marijuana patients cut back on their use of another prescription drug after getting a cannabis card.

And 42 percent stopped taking a pharmaceutical altogether.

'People are not only self-medicating but they're self un-medicating,' says Dr Kruger.

For the 26 percent of study participants that weaned themselves off of potentially dangerous drugs like OxyContin, it's likely for the best.

But doing so without the knowledge or guidance of a primary care provider could pose serious dangers.

'My concern is that we're back to the mid-19th Century with people running around selling "cure-alls," these tincutures that often have high potency,' says Dr Kruger.

'But we don't have the evidence-basedscience that is required for a standard pharmaceutical to see what this is effective at treating.'

Being a Schedule 1 drug means that there is limited research scientists can legally conduct, let along get funded.

'It's so illegal at the federal level that basically researchers still have one hand tied behind their backs and a giant boxing glove on the other,' says Dr Kruger.

and there is no standardization for what compounds can be present at what dosages in cannabis products.

'It's like if a physician handed you a bag of pills of all different colors, shapes with maybe some numbers on them and they said "here, take them until you feel better."

'That's effectively the state we're in,' says Dr Kruger.

The University of Michigan study, published in the Journal of Psychoactive Drugs, only addressed conditions that marijuana is generally recommended to treat in comparison to traditional drugs approved to treat those same conditions.

It's worth noting, however, that some patients incorrectly believe that cannabis can treat conditions like cancer itself - not just side effects of chemotherapy, like nausea.

A study published last year found that more than 20 percent of people who have or had cancer believe that alternative therapies can cure or prevent cancer, as do nearly 40 percent of caregivers to cancer patients.

There is decades of research demonstrating that cannabis can help chemo patients cope with nausea improve their appetites. There is very little to suggest it has any worthwhile effects on cancer itself.

While many doctors recommend it as a complementary treatment to traditional, tested cancer treatments, cannabis is not considered an actual cancer treatment.

And, as the University of Michigan study authors note, because marijuana is still illegal on the federal level, studies on its effects to prove just about any claims about the substance struggle to get funding.

The distinction between alternative and complementary medicine may not always be clear to patients, especially when they are faced with traditional treatments that are not delivering the results they hoped for and are draining their bank accounts.

The same 2018 study on alternative medicines found that 57 percent of Americans are worried they won't be able to afford cancer treatments.

And in the new University of Michigan study, most patients saw medical marijuana is more cost-effective than traditional pharmaceuticals, though this had less bearing on their preference for it than other advantages like its minimal side effects.

Whatever their motivations, it's clear that more and more Americans are and will flock to medical marijuana.

The first step to making sure is safe to do so is to change the drug scheduling of marijuana, according to Dr Kruger.

'The science of the practice has not kept pace with the very rapid legal changes,' he says.

'All policy should be driven by science,' but right now 'there's a lack of integration of these systems' of the medical cannabis industry, the law, clinicians and public health policy.

'And integration of these systems is what we're pushing for,' Dr Kruger says.