At a time when the U.S. grapples with the question 'What Is Truth?', the story of cannabis prohibition should be an object lesson in what happens when a culture doesn't care what the truth is. The object lesson: one day, it will.

We need only to look to the story of Harry Anslinger, who in 1930 became America's first commissioner of narcotics, a position that allowed him to paint a picture of marijuana's supposed evils that continues to color public perception today.

Bias appears in subtle ways, particularly in word choice. We know – empirically – that cannabis affects everybody differently. It would be inaccurate to say one person's experience with the drug is exactly like the next person's.

It would be easy to assume that Anslinger enacted marijuana prohibition because of proven concerns about harm to public health. Anslinger helped stifle the research that might have supported his assumption that marijuana posed a health hazard. From the start of his administration onward, the federal government refused to allow any federally funded testing on cannabis.

However, a legitimate case can be made that racism was always behind Anslinger's actions.  When he was appointed as the founding commissioner of the Federal Bureau of Narcotics — America's first narc — he took over a bureau with no money, no manpower, and no mandate; all narcotics were legal. Of all the drugs under his purview, Anslinger singled out marijuana as the most dangerous, though even then all evidence was to the contrary. Using his own soon-to-be-evident racism as a guiding principle, Anslinger also refused to accept the truth or the word no in his relentless quest to make marijuana illegal and to punish the people who used it.

To determine whether cannabis is harmful to us, first, we have to try and figure out who, if anyone, is telling the truth about it.

The dictionary definition of empirical truth, the most verifiable kind, is, “exact conformity as learned by observation or experiment between judgments or propositions and externally existent things in their actual status and relations — called also actual truth.. If the subject under discussion were acid reflux and a pharmaceutical product that easily dealt with it, this would be a far simpler conversation for us to have. The topic is cannabis, however, and the body part it most evidently acts upon is our brains where subjectivity rules.  Conversations get harder.

Getting to empirical truth gets harder, too.

The late Booker Prize-nominated English historian and author Martin Booth, writing in “Cannabis: A History,” describes how as far back as 10,000 years ago, humans began their relationship with cannabis, most likely in eastern Asia, where ample evidence of that relationship has been found in pottery shards, tombs, and even silk scarves are interwoven with hemp thread. Hemp and cannabis and their relationship with humans spread from there.

The idea of making cannabis illegal is a fairly recent phenomenon, scholar Barney Warf told Prohbtd. Warf, a professor at the University of Kansas in the Geography and Atmospheric Science Department, studies how people have moved around the planet. He's concluded that cannabis has a long history within many cultures, including the ancient Greeks.

According to Warf, “It's really in the moral panic of the early 20th century that it becomes demonized. … I think all its history and geography reflect its centrality to many cultures, and the idea that there's something bad about smoking it is a more or less uniquely American kind of interpretation that then became globalized.”

For most of its history, cannabis was not only legal but also tolerated and even actively promoted by empires and corporations, such as the British East India Company.

However, it's more difficult to determine when humans first realized that cannabis had psychoactive properties. There are illuminating blips in the historical record. Back to Booth, who describes the story of Haydar, founder of the Persian Sufi Hyderi sect.  A monk living a simple life, Haydar returns from a walk in the countryside with a smile on his face and in a “capricious mood.” The usually reserved monk had encountered a marijuana plant and he became fascinated by its ability to withstand the heat. Legend has it that as he walked on, he chewed on the plant's leaves – and, according to Haydar's chronicler “…remained in a capricious mood until his death 66 years later.”

So, we can conclude that the capricious mood did not kill him. Or, if it did kill him, it took 66 years to do it.

Meanwhile, every time that Haydar chewed those cannabis leaves, the THC supposedly found its way into his bloodstream and his brain where the THC's psychoactive properties went to work.  But what do we mean by went to work?” According to the National Institute On Drug Abuse, THC's chemical structure is similar to the brain chemical anandamide. Our brains recognize this chemical and readily bond with it. But that's from THC's point of view.

Let's look at it from our brains' point of view.

What are thoughts: Thoughts are generally considered to be the product of chemicals traveling between paths of neurotransmitters, which are like digital switches; they're either open or closed. Open: They're able to receive incoming chemical information. Closed: They're not able to receive that information.

As anyone who has ever experienced how THC feels – that additional data flowing through your brain heightens sensory perceptions. THC can make food taste incredible. It can make light look transcendent. It can make friend's last statement profound. It can make something mildly amusing seem like comedy gold. Some of us feel as if we see more, hear more, take in more. Some people, by contrast, find that increased information flow unpleasant or distracting; it makes them feel paranoid even while their friends are blissed out beside them.

Those are the experiential effects most cannabis users recognize. For most marijuana users, very little reliable data exist at present that says cannabis is hurting their brains, though the drug can affect certain populations. There are data that suggest marijuana use can exacerbate or accelerate psychosis in marijuana users who are predisposed genetically or circumstantially.  But – causal links are harder to come by. As the authors of a review of studies for The International Journal of Drug Policy point out: “Few studies have evaluated the relative strengths and limitations of these methodologically heterogeneous cohort studies, and how their relative merits and weaknesses might influence the way the link between cannabis use and psychosis is interpreted.”

Even smoking cannabis, at present, is “not linked to cancer,” according to the Centers for Disease Control and Prevention,” which found that, “more research is needed to know if smoking cannabis increases a person's risk for lung cancer. However, it is difficult to determine whether there is a link, because cannabis use often overlaps other behaviors related to lung cancer, such as tobacco use.”

The one real battleground seems to be the brain. Some studies have shown cannabis can exacerbate or trigger psychosis.Another study links conditions like bipolar disorder and schizophrenia to premature brain aging; it sees a similar link between alcohol and cannabis users. An Australian study found that cannabis use can disrupt the effectiveness of some treatments for schizophrenia (while not interfering with others). It's brain chemistry. It's complicated. There are people for whom cannabis would be a poor choice – of medicine or recreational drug. Their brain chemistry and THC probably shouldn't be together.

Given that prohibition prevented extensive cannabis research, the only thing that scientists and legislators can say with certainty is that we need more research into cannabis and its effect on the brain. Without sufficient research, experts can't say for certain that cannabis causes its users to take unnecessary and dangerous risks, nor can it or has it incontrovertibly compared those actions with alcohol. The law, however, treats cannabis as if alcohol and THC impacted the user's cognition in exactly the same way, even though they are different chemicals entirely.

In its report “Marijuana Impaired Driving,” the National Highway Transportation Safety Administration (NHTSA) noted that the effects of THC on cognition — as opposed to behavior —  is still under debate. Yet even as it described marijuana use as “impairment,” it also found that alcohol users become more dangerous drivers, but cannabis users drive more carefully as a result of having consumed THC. Evidently, cannabis users compensate for their “impairment” by driving more cautiously.

NHTSA concluded that  the current state of research on cannabis and its impact on operating a motor vehicle “does not show a relationship between THC levels and impairment.”

One more statistic that flies in the face of conventional wisdom and how cannabis actually affects people: medical cannabis use does not increase the likelihood that a user will be in our cause a vehicular crash.  Clearly, THC cannot be impairing cannabis users the same way alcohol affects drinkers. Why then do we still treat it and criminalize it like it did have the same effect? The National Organization for the Reform of Marijuana Laws (NORML) has compiled a list of well-documented scientific research on marijuana and driving.

In the absence of enough data to form a scientific consensus we can't answer the question “What does cannabis do to the people who use it?”  To answer, you would have to ask every cannabis user. That's not meant to be flippant: Anecdotal uses of cannabis provide the biggest data pool we have.

When you read a lot of what gets written about cannabis, one thing becomes clear: when it comes to cannabis and how people experience cannabis, cannabis users usually know what they're talking about far more than non-users. It's that subjective and experiential.

So, what is the straight dope on dope?  Because of how THC works in our brains, it's probably isn't a good medicine or recreational drug for some people with certain brain chemistry issues.  More research is needed. For most other people however, little to no data exist that says marijuana is in any way profoundly harmful or bad for you. Vastly more data say that marijuana is efficacious as a medication for a variety of ailments – medical and otherwise.

There simply never was a 'medical' – or moral – reason to make marijuana illegal.