Today, research on the effects of psychedelics is one of the most exciting fields of psychology. The US Food and Drug Administration recently approved a clinical trial to test if the psychedelic compound in ecstasy can treat PTSD; psilocybin, the key ingredient in magic mushrooms is now considered a promising treatment for depression; and studies suggest that LSD could help combat alcoholism. There’s still plenty of red tape and skepticism, but it feels like scientists are well on their way to establishing the health benefits of these powerful drugs.

It feels terribly cutting edge, but such research is, in fact, old. Before LSD became a party drug, it was used to treat conditions like alcoholism, PTSD, and depression. And, as a new documentary on Cary Grant explores, the actor was one of the first to experience LSD in a psychiatric setting.

According to the film, Becoming Cary Grant, the actor first tried LSD at the Psychiatric Institute of Beverly Hills in 1958 and took the drug 100 times over the following three years. He was effusive about the results, as Vanity Fair reports, telling Look magazine in 1959, “at last, I am close to happiness.” He viewed the treatment as a way of resolving childhood trauma and coming to terms with the ends of difficult marriages; after starting his LSD treatment, Grant realized, “all my life, I’ve been going around in a fog.”

Though LSD had been used as treatment for a few years previously, Grant’s enthusiasm helped popularize the then-little-known drug. In total, from 1950-1965, around 40,000 patients were prescribed LSD to treat a variety of conditions. The drug was little known at first but gradually increased in popularity before US drug safety regulations began to restrict its use in 1962. In 1966, possession of the drug was made illegal in the US.

The backlash against LSD—partly attributed to negative experiences of the drug, or bad trips, and partly to its association with the political counterculture of the time—was closely linked not just to its recreational use, but also the lack of rigor around psychological research at the time. Timothy Leary, a Harvard psychologist who was studying the psychological effects of psychedelics in the late 1950s and early 1960s, was not allowed to continue working at the university in 1963, in part due to his sloppy research. Leary was accused of giving psychedelics to undergraduates without medical supervision and, after leaving academia, went on to promote psychedelics with the phrase, “Turn on, tune in, drop out.” Then-president Richard Nixon reportedly called him “the most dangerous man in America.”

But though early research in LSD as therapy has a decidedly mixed reputation, Robin Carhart-Harris, head of Psychedelic Research at Imperial College London, says that much of the work undertaken in the 1950s and ‘60s was actually quite strong.

“It’s easy for us to be derogatory about the old research but they were asking all the questions we’re asking now,” he says, “Perhaps the methods weren’t as tight as they are today but, even so, there was a fair amount of good work.”

Today, he says researchers are “more privileged.” Brain imaging has been instrumental in navigating the effects of psychedelics and there are now standard rating scales for measuring depression, for example, as well as careful placebo control procedures and a greater awareness of biases.

Carhart-Harris says he and his colleagues occasionally read through older literature. It can feel reassuring, he says, to see that the effects they’re finding today were also noted decades ago.

“In a way we’re re-inventing the wheel, but we’re doing it with the knowledge and methods we have now,” he says. “You can think of the old literature as being quite extensive and rich but also a little loose and quite poetic.”

Herbert Kleber, professor of psychiatry and substance-abuse researcher at Columbia University, notes that the smaller doses used today are far safer than in previous decades. While working on narcotics addiction at the US Public Health Service Hospital in Lexington, Kentucky (now called the Federal Medical Center) in 1965, Kleber conducted research into LSD’s potential as a treatment treatment for addiction.

He did not get far in his research, and though he believed there were early signs that the drug could be useful for breaking addiction cycles, he also saw plenty of bad trips. “I remember there was a painting on the wall and under the influence of LSD, one patient [in the study] saw the painting come off the wall and chase him around the room,” he says. “Another one tried to break down a door because he was convinced his wife was on the other side and we were keeping her from him.” Kleber was interested in testing the drug at a lower dose, he says, but LSD was banned soon after.

Despite the downsides, researchers were uncovering the potential value of LSD. Carhart-Harris points out that prominent figures such as senator Robert F. Kennedy were supportive of the research, and went to bat for LSD in Washington, DC. “If they [LSD experiments] were worthwhile six months ago, why aren’t they worthwhile now?” Kennedy asked the FDA in 1966, after research on the drug was banned. “Perhaps to some extent we have lost sight of the fact that [LSD] can be very, very helpful in our society if used properly.”

But research into the medical benefits of psychedelics stalled in the late 1960s. “[Cultural attitudes] are very powerful and they stick,” says Carhart-Harris. “We’re the victims of that, and so are patients to some extent—victims of this stigma and misinformation.” As a result, there are no approved medicinal uses for LSD, but both Kleber and Carhart-Harris agree there’s evidence the research should continue. “If you have a compound that seems to be beneficial, works in a novel way, and does something different than currently available treatments, then you could really question the ethics of withholding funding,” says Carhart-Harris.

The good news is that, thanks in part to tighter research methods, government agencies are starting to loosen up restrictions on studying psychedelics. Psychologists are now picking up a decades old experiment. “We’re both catching up and advancing,” adds Carhart-Harris.

But there’s no guarantee that the trend will hold. “I don’t want to be too naive and say, ‘it’s just not going to happen this time because we’ve learnt from the mistakes of the past,’” says Carhart-Harris. After all, he adds, in politics, “anything can happen.”