25 million people take Adderall to help them focus. But when used recreationally, the drug can be harmful—even deadly.

By the time 36-year-old Scott Hahn caused a fatal crash on the New Jersey Turnpike Feb. 22, he'd taken 10 Adderall pills and been awake for more than a day. The accident took the lives of local teacher Tim O'Donnell and his 5-year-old daughter Bridget and revived old concerns about the drug's link to erratic behavior.

Those present in the minutes before the crash say Hahn was swerving in and out of lanes and driving erratically in the moments before the crash, when he sent O'Donnell's car flying into the eastbound lane. Now he faces up to 30 years in prison for aggravated manslaughter and vehicular homicide, his story is a reminder of the dangers of stimulants.

Amphetamines come with a host of negative side effects, most commonly insomnia and irregular heartbeat. But in less common cases, the drug can induce a psychosis that is nearly identical to schizophrenia—so close, in fact, that scientists use it to study the disease. Far from a new discovery, it's something that scientists and pharmaceuticals have known about for decades.

Adderall was officially approved by the Federal Drug Administration (FDA) in 1960 and has, in recent years, become ubiquitous. From the years 2002-2006, sale of the drug increased by an estimated 3000 percent. In 2010 alone, 18 million prescriptions for Adderall were issued—a surge that has put significant pressure on drugstores.

The Drug Enforcement Administration (DEA) lists it as a schedule II substance, with the likes of cocaine and oxycodone. As the amounts of prescriptions have increased, pharmacies have struggled to keep up with demand. In 2015, 96 percent of pharmacies reported shortages of the drug in the previous month.

Today, according to the American Chemical Society (ACS), an estimated 25 million people worldwide take amphetamines to help them focus. While effective at improving the lives of those suffering from attention disorders, the drug can be dangerous for those who use it recreationally.

In a video on ACS, neurologist Dr. Ryan Davison explains why the drug affects individual brains differently. "People with ADHD tend to have lower levels of dopamine—a key chemical in the brain's reward center," says Davison. "This lack of dopamine means people with ADHD are constantly seeking stimulation."

To counter this, amphetamines release dopamine and other neurotransmitters, stimulating the central nervous system and allowing the person to focus.

But despite the positive benefits of the drug, tragedies like the O'Donnells' suggest there's another part of the story that's missing. For those without attention disorders, whose dopamine levels are normal, the surge of the reward center chemical can trigger anxiety and euphoria.

But even in those who need the drug, it can be problematic.

According to a wealth of research, Adderall can be the precursor to hallucinations, delusions, and full-blown psychosis—one so similar to schizophrenia that doctors use it to study the disease. The drug's connection to psychosis dates back to its earliest uses.

Amphetamines, despite their modern popularity, have been around for more than a century.

A Romanian chemist named Lazăr Edeleanu is credited with synthesizing the drug at the University of Berlin in 1887, using an ingredient from a Chinese flower. It wasn't until 40 years later that American chemist Gordon Alles uncovered the psychological effects of the drug.

His discovery would turn out to be a lucrative one when American pharmaceutical Smith, Kline, & French (now GlaxoSmithKline) purchased the patent and began selling it over the counter for congestion in 1932. The drug was an immediate hit and marketed as a treatment for a variety of conditions, from anxiety to narcolepsy.

Once in pill form, the drug became a popular choice for soldiers and shift workers who needed to stay alert long into the night. By the early 1960s, the FDA reported that there were at least 200 million amphetamines pills circulating in the U.S. It was a few years later, in the mid-'60s, that some began to express concern about the drug's negative effects.

One of the earliest warnings is a letter by P.H. Connell published in the British Medical Journal on March 9, 1957. After highlighting what he viewed to be "widespread abuse" of the drug, Connell flagged a dangerous side effect. "A common result of amphetamine intoxication is the development of a paranoid psychosis indistinguishable from schizophrenia, during which the patient may be a serious social danger," he wrote.

His work was bolstered by 1965 study in the British Journal of Psychiatry, which compared schizophrenia with amphetamine-fueled psychosis. In it, scientists detailed 14 cases in which the amphetamine psychosis resembled schizophrenia so closely that they were near impossible to tell apart.

"Amphetamine psychosis, and psychoses due to other stimulants, present as a well-defined syndrome of a paranoid state with auditory and visual hallucinations in a setting of clear consciousness," the study's authors wrote. After comparing the two, the scientists concluded, "amphetamine intoxication can precipitate the onset of a schizophrenic episode."

In 1971, two scientists published what has become one of the seminal studies on the topic. In the Journal of American Medical Association, they observed psychosis in two children who were taking methylphenidate (Ritalin)—one taking a prescribed dose, the other taking an elevated amount.

Comment: More about Ritalin Gone Wrong:
To date, no study has found any long-term benefit of attention-deficit medication on academic performance, peer relationships or behavior problems, the very things we would most want to improve. Until recently, most studies of these drugs had not been properly randomized, and some of them had other methodological flaws.
The Over-Prescribing of Psychoactive Drugs to Children is very concerning, considering the information above, there appears to be no long term benefits from attention-deficit medications. Big Pharma-funded doctors are making a killing prescribing questionable drugs to young children:
Big Pharma has spent millions on public relations campaigns that tell parents, teachers and clinicians to dose children at the first sign of problems. It knows if parents treat their kids early they will never know if the kids needed the drugs in the first place and whether residual problems are "mental illness" or drug side effects. The kids will also probably be life long customers because parents will be afraid to take them off the drugs. No wonder Pharma tells parents not to wait for "excessive energy" or "mood swings" to go away in the awareness campaigns. Ka-ching.

One of the many recent studies on the phenomenon was published in the American Journal of Psychiatry in 2006. "Stimulant medications at high doses can induce symptoms of mania and psychosis that are highly similar to those of bipolar or schizophrenic illnesses," the authors wrote. "These symptoms generally resolve within two days after discontinuation of the stimulant, although symptoms lasting six days or longer have been reported."

Nick Rasmussen, a historian at the University of New South Wales, in Sydney, wrote an authoritative and popular book on the topic in 2008 titled On Speed: The Many Lives of Amphetamine. Rasmussen says that amphetamine-induced psychosis has been an "indisputable medical fact" since the '50s.

"The facts that made this clear at the time were that lots of people with schizophrenic symptoms turned out to be heavy amphetamine users (many of whom started with medical not recreational use but became addicted)."

Rasmussen says the main difference between the two was that one ended when the amphetamines were stopped. "After a few days in the psych ward cut off from speed [they] became totally normal. This does not happen with schizophrenia."

Rasmussen says the similarities between amphetamine-induced psychosis and actual mental illness are so comparable that doctors use them to study each other.

"Amphetamine psychosis was such an established fact that by the 1960s amphetamine-crazed rodents became a standard experimental model of schizophrenia for neuroscientists," he says. "They use such experimental animals to look for new antipsychotic drugs."

While drug companies have known about the potential for psychosis since the 1950s, the fact hasn't become common knowledge. Rasmussen says consumers don't know enough about the risks of Adderall in part because of what drug companies call "opinion leaders"—physicians who create "research-cum-marketing materials" for doctors.

It's not as if attempts to promote the safety of drugs are not made. Doctors are required to take continuing education courses and the FDA frequently carries out reviews of drugs. One particularly damning review for Adderall came in March 2006, when Dr. Kate Gelperin and Dr. Kate Phelan published the drug's adverse affects associated with treatment of ADHD.

Their main concern was amphetamines' potential to induce psychosis, and the lack of adequate warnings on the label. Not long after, the drug's label was revised to include a boxed warning about the potential for abuse, aggression, and psychosis.

As use of Adderall becomes more widespread, public battles have begun coming to the forefront—most recently with Scott Stapp, the lead singer of Creed. Stapp, who was diagnosed with bipolar disorder, recounted his struggles with Adderall in an interview with Oprah. "I began taking a prescription drug called Adderall and I went into a full-on psychosis and had a psychotic break," he says of the experience, which was likely exacerbated by his bipolar disorder. "It was horrific, the experience."

Expanding further in an interview with Nightline last May, Stapp recalled vivid delusions that his wife was trying to poison him, that the White House was trying to send him messages, and that the CIA wanted him dead. At one point he called his son's school to report that ISIS was at the "center of his family."

Now clean after a second relapse, Stapp hopes to spread awareness about mental illness and the dangers of amphetamines, which—although not necessarily connected—undoubtedly share patterns.

Rasmussen, who spent years studying Adderall and other amphetamines for his book, seems still at a loss when it comes to a solution. When I ask why doctors are still prescribing a drug this dangerous, his response is two words: "Why indeed."