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Potential treatments for Alzheimer’s disease, cancer and many other illnesses are being blocked by anti-drug laws, according to a new editorial review published in Nature Reviews Neuroscience.

Lead author David Nutt, chair of neuropsychopharmacology at Imperial College London, and his colleagues argue that tight restrictions on research on illegal drugs like marijuana and “legal highs” are hindering progress in neuroscience and deterring drug companies from pursuing important leads in major disorders affecting millions of patients. Nutt lost his job as the top advisor to the British government on drug policy in 2009 for publicizing data showing that ecstasy (MDMA) is less harmful than drinking or horseback riding.

Comparing the harm to science to that done by the Catholic Church in banning the works of Gallileo and Copernicus, Nutt says, “People have not even realized how much research and how many possible new treatments have been blocked by drug laws.”

Marijuana research, for example, is still extremely difficult to carry out — despite legalization of medical use by 17 states and recreational use by two. In the U.S., the drug can only be legally obtained for study from the National Institute on Drug Abuse and requires a special review and FDA-approved protocols that are not needed to study legal drugs or most experimental compounds. In the U.K., ironically, it is easier to study heroin than marijuana because heroin is a legal painkiller there.

And yet the research that has been done on cannabis suggests significant promise— beyond relief of pain and nausea, where the benefits have already been clearly demonstrated.

For one, several studies now suggest that marijuana might fight diabetes and obesity, two of today’s top public health threats. Secondly, other research suggests that cannabinoids— substances found in marijuana or synthetic versions of them— might potentially prevent Alzheimer’s disease, another leading cause of disability and death. Finally, there are dozens of studies showing activity of cannabinoids against various cancers.

(MORE: How Cannabinoids May Slow Brain Aging)

As a recent review of the cancer research put it:

[Anti-cancer] activities have been demonstrated.. for various malignancies, including brain, breast, prostate, colorectal, skin, thyroid, uterine cervix, pancreatic cancer, leukemia, and lymphoid tumors.

Says Nutt, “Inadvertent consequences of drug laws set up to stop people coming to harm failed to do that and inadvertently really screwed over research.”

The illegality of recreational drugs in combination with the globalization of manufacturing and the internet has also led to the creation of a murky market in “legal highs.” Here, experimental compounds that seem likely to have pleasant effects are copied from pharmaceutical patent applications and research papers, then marketed without safety testing, even on animals. Governments then race to ban whatever gets media attention for becoming popular or doing harm, which sends illicit chemists back to the lab to make new “legal” products.

The arms race means that many substances are banned with little or no study— and there are no published standards to determine what should be illegal. The effect is to hinder legitimate research, making many molecules as hard to study as marijuana. The expense and the hassle deter both academic and pharmaceutical industry researchers.

“It increases the cost of my research by between 5 and 10 times,” says Nutt, who is one of the few who holds licenses to do such work in humans. He notes that the two co-authors on his paper are both retired and says that one colleague wanted to co-write it but didn’t for fear of losing future government funding. “Active researchers are terrified,” he says.

As a journalist who has covered this area for decades, I’ve seen this problem occur repeatedly. Over the years, many researchers, who refused to be quoted publicly, have privately expressed to me their frustration with the barriers on research and one told me explicitly that he dropped a promising line of work on a major disease because of them.

The review notes numerous examples of the laws’ interference with medicine. For one, virtually all psychedelic research was shut down after LSD became popular in the 1960’s, despite data suggesting it was promising for the treatment of alcoholism and useful in therapy. Now, new data from the few small studies that can get funded suggest that psilocybin mushrooms may help treat obsessive-compulsive disorder and MDMA may fight post-traumatic stress disorder and Parkinson’s disease.

(MORE: LSD May Help Treat Alcoholism)

Another example is the story of methoxetamine, a compound similar to ketamine. Ketamine is legally used for anesthesia and is now showing promise as a rapid-acting antidepressant. But it is also misused recreationally, typically in nightclubs. Long term recreational use— and possibly long term therapeutic use— can cause bladder damage, sometimes severe enough to require the removal of the organ.

Methoxetamine, however, seems to have the positive effects of ketamine, without the bladder risk. But because it has been used as a “legal high” and substitute for ketamine, the British government banned it this year, along with similar compounds that might also have therapeutic benefit.

“That means there won’t be much research on safer alternatives to ketamine,” says Nutt, “People will stick to ketamine and run the risk of bladder [problems]. What’s worse, some of the compounds, which have been banned were never tested in humans or never even made. This is again like locking away science so people will never explore the full potential of these compounds.”

(MORE: ‘Magic Mushrooms’ Like ‘An Anti-Inflammatory for the Ego’)

Right now, there are no clear answers as to how to solve the regulatory dilemma. Three United Nations treaties limit how countries can change their own laws in relation to currently illegal drugs; and although public opinion is changing on marijuana, federal law in relation to its medicinal uses has been remarkably resistant to change.

The UN will meet to review its drug policies in 2016 and that’s where Nutt would like to see revisions. “We’ve got to have evidence-based drug classifications and policies,” he says.

The problem varies by drug. Marijuana, for example, has not been categorized by the U.N. as entirely without medical use, while MDMA and psilocybin were declared medically useless. This means that America could unilaterally decide to make medical marijuana legal, putting it in a category with drugs like morphine, that are restricted but are not as difficult to study— but changing the status of other drugs would require international cooperation.

And as the “legal high” market grows and chemists become ever more clever, the current system of regulation is being overwhelmed. We all want to prevent addiction and the negative consequences associated with the use of some drugs — but, as this review demonstrates, it is becoming increasingly clear that the main type of experimentation that our drug laws prevent is legitimate scientific research.