This is Part One of our Psychedelic Science series. Click here for Part Two, here for Part Three, and here for Part Four.

Research into the therapeutic potential of illegal "psychedelic" drugs to treat an assortment of mainstream mental health conditions is undergoing a modern-day renaissance.

A host of published studies in the field is showing promise for psychedelics, such as psilocybin — the active ingredient in "magic mushrooms" — to help treat alcoholism, depression, drug addiction and severe anxiety caused by serious or terminal illness.

Other studies are finding that MDMA, also known as the party-drug "ecstasy," may be valuable in treating Post Traumatic Stress Disorder (PTSD).

"These drugs ... were researched extensively in the 1950s and the 1960s, through the early '70s," says Dr. George Greer, medical director for the nonprofit Heffter Research Institute, which raises donations for psilocybin studies worldwide. "There were hundreds of studies that were very promising."

But the psychedelic '60s changed all that.

LSD and other hallucinogens, once confined to the lab, exploded into mainstream culture after the pied-piper of psychedelics, Timothy Leary, urged a generation to try LSD and other hallucinogens as a way to "turn on, tune in, drop out." Many followed his advice, some with bad results. And that triggered a backlash that led the federal government to criminalize psychedelic drugs in 1970.

A year later, President Nixon launched the "War on Drugs."

Those measures helped to create a stigma that brought an end to the early phase of psychedelic research, says Rick Doblin, founder the Multidisciplinary Association for Psychedelic Studies (MAPS).

"There is this tendency when drugs become criminalized for their non-medical use, their medical use then subsequently also becomes suppressed," says Doblin.

But since early 2000, a new willingness to look again at these drugs has shifted the research landscape. And thanks to the fundraising efforts of MAPS and the Heffter Research Institute, modern-day psychedelics studies are now happening at top academic research facilities, including Johns Hopkins University, New York University, the University of New Mexico and UCLA.

"These agents have very broad applicability within psychiatry and can be used for mood disorders, eating disorders, personality disorders," says Dr. Stephen Ross, a psychiatrist and psychedelics researcher at NYU School of Medicine. "They can be used for so many things that our treatment have not improved in recent years."

But the drugs are powerful and must be used with caution, especially since it's believed they can exacerbate serious mental conditions, such as bipolar disorder and schizophrenia. However, used in a supervised setting with trained therapists, these drugs have the potential to offer properly-screened patients much-needed new treatment options.

"We are not at all referencing our work to the recreational drug-use world, which is rife with potential risks," says Dr. Charles Grob, director of the Division of Child and Adolescent Psychiatry at Harbor-UCLA Medical Center and a pioneer in modern-day psychedelics research. "We are talking about developing a new model ... to be used within medicine and psychiatry."

Grob says psychedelics offer a rather unusual paradigm in which many patients are reporting relief with as few as one or two supervised applications of the drugs, used in conjunction with limited psychotherapy.

"This is very different than conventional drug treatment, which, more often than not, administers a drug on a daily basis for weeks, months and even years," Grob says.

And research into these drugs is a bit less conventional as well. Because the Drug Enforcement Agency (DEA) classifies these illegal drugs as "Schedule One" substances — considered risky with "no currently accepted medical use" — scientists must adhere to strict protocols when researching them. Those include rules on how the drugs are used, handled and stored.

But a greater challenge remains financing. So far, the government has yet to fund research into psychedelics. That leaves private donations as the sole source of funding.

Scientists in this field say they believe as more evidence into the varied uses for these drugs is collected and published the government will be more likely to grant research funding requests.

And as more time passes, Grob says, the stigma brought on by the excesses of 1960s counterculture will further fade.

"The '60s are long over. As the Moody Blues used to sing, 'Timothy Leary is dead'…and many of those with whom he fought have also exited," Grob says, "It's a new world and there is a greater need than ever for more effective treatment models for individuals for whom our conventional treatment models are often sorely lacking.