In 1967, because of my concern about the rapidly growing use of the dangerous drug marijuana, I began my studies of the scientific and medical literature with the goal of providing a reasonably objective summary of the data which underlay its prohibition.

Much to my surprise, I found no credible scientific basis for the justification of the prohibition. The assertion that it is a very toxic drug is based on old and new myths. In fact, one of the many exceptional features of this drug is its remarkably limited toxicity. Compared to aspirin, which people are free to purchase and use without the advice or prescription of a physician, cannabis is much safer: there are well over 1000 deaths annually from aspirin in the United States alone, whereas there has never been a death anywhere from marijuana.

In fact, when cannabis regains its place in the US Pharmacopeia, a status it lost after the passage of the Marijuana Tax Act of 1937, it will be seen as one of the safest drugs in that compendium. Moreover, it will eventually be hailed as a “wonder drug” just as penicillin was in the 1940s. Penicillin achieved this reputation because it was remarkably non-toxic, it was, once it was produced on an economy of scale, quite inexpensive, and it was effective in the treatment of a variety of infectious diseases. Similarly, cannabis is exceptionally safe, and once freed of the prohibition tariff, will be significantly less expensive than the conventional drugs it replaces while its already impressive medical versatility continues to expand.

Given these characteristics, it should come as no surprise that its use as a medicine is growing exponentially or that individual states have established legislation that makes it possible for patients suffering from a variety of disorders to use the drug legally with a recommendation from a physician.

Unfortunately, because each state arrogates the right to define which symptoms and syndromes may be lawfully treated with cannabis, many patients with legitimate claims to the therapeutic usefulness of this plant must continue to use it illegally and therefore endure the extra layer of anxiety imposed by its illegality.

California and Colorado are the two states in which the largest number of patients for whom it would be medically useful have the freedom to access it legally. New Jersey is the most restrictive, and I would guess that only a small fraction of the pool of patients who would find marijuana to be as or more useful than the invariably more toxic conventional drugs it will displace will be allowed legal access to it. The framers of the New Jersey legislation may fear what they see as chaos in the distribution of medical marijuana in California and Colorado, a fear born of their concern that the more liberal parameters of medical use adopted in these states have allowed its access to many people who use it for other than strictly medicinal reasons. If this is correct, it is consistent with my view that it will be impossible to realize the full potential of this plant as a medicine, not to speak of the other ways it is useful, in the setting of this destructive prohibition.

Marijuana is here to stay; there can no longer be any doubt that it is not just another transient drug fad. Like alcohol, it has become a part of our culture, a culture which is now trying to find an appropriate social, legal and medical accommodation. We have finally come to realize, after arresting over 21 million marijuana users since the 1960s, most of them young and 90% for mere possession, that “making war” against cannabis doesn’t work anymore now than it did for alcohol during the days of the Volstead Act.

Many people are expressing their impatience with the federal government’s intransigence as it obdurately maintains its position that ” marijuana is not a medicine”. Thirteen states have now decriminalized marijuana. And, beginning with California in 1996, another 15 states and the District of Columbia have followed suit in allowing patients legal access to marijuana, and others are in the process of enacting similar legislation. These states are inadvertently constructing a large social experiment in how best to deal with the reinvention of the “cannabis as medicine” phenomenon, while at the same time sending a powerful message to the federal government. Each of these state actions has taken a slice out of the extraordinary popular delusion known as cannabinophobia.

Perhaps in part because so many Americans have discovered for themselves that marijuana is both relatively benign and remarkably useful, moral consensus about the evil of cannabis is becoming uncertain and shallow. The authorities pretend that eliminating cannabis traffic is like eliminating slavery or piracy, or eradicating smallpox or malaria. The official view is that everything possible has to be done to prevent everyone from ever using marijuana, even as a medicine. But there is also an informal lore of marijuana use that is far more tolerant.

Many of the millions of cannabis users in this country not only disobey the drug laws but feel a principled lack of respect for them. They do not conceal their bitter resentment of laws that render them criminals. They believe that many people have been deceived by their government, and they have come to doubt that the “authorities” understand much about either the deleterious or the useful properties of the drug. This undercurrent of ambivalence and resistance in public attitudes towards marijuana laws leaves room for the possibility of change, especially since the costs of prohibition are all so high and rising.

It is also clear that the realities of human need are incompatible with the demand for a legally enforceable distinction between medicine and all other uses of cannabis. Marijuana simply does not conform to the conceptual boundaries established by twentieth-century institutions. It is truly a sui generis substance; is there another non-toxic drug which is capable of heightening many pleasures, has a large and growing number of medical uses and has the potential to enhance some individual capacities?

The only workable way of realizing the full potential of this remarkable substance, including its full medical potential, is to free it from the present dual set of regulations – those that control prescription drugs in general and the special criminal laws that control psychoactive substances. These mutually reinforcing laws establish a set of social categories that strangle its uniquely multifaceted potential. The only way out is to cut the knot by giving marijuana the same status as alcohol – legalizing it for adults for all uses and removing it entirely from the medical and criminal control systems.

Lester Grinspoon, M.D. is Associate Professor of Psychiatry, emeritus, at Harvard Medical School and the author of Marihuana Reconsidered and (with James B Bakalar) Marijuana, the Forbidden Medicine.

Dr. Grinspoon recently endorsed the Regulate Marijuana like Wine Act of 2012 to legalize marijuana in California. Read more on Cannabis Culture