A new study sheds light on a rare but potentially dangerous risk of commonly-used medications to treat attention-deficit/hyperactivity disorder (ADHD). Researchers evaluated the two most common types of ADHD medications and found that, while the risk is low, certain drugs have an increased risk of psychosis.

"We looked at new users, people who are being prescribed these medications for the first time," Lauren V. Moran, MD, a psychiatrist at McLean Hospital who led the study, told CBS News. "We compared amphetamines, which is Adderall and Vyvanse, to people who were prescribed methylphenidates, which is Ritalin or Concerta. "We found that the Adderall-type drugs had an increased risk of psychosis."

Rates of ADHD have been rising sharply in recent years. More than 6 million U.S. children and teens have been diagnosed with the disorder, which is characterized by attention difficulty, hyperactivity, and impulsiveness, according to the Centers for Disease Control and Prevention.

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Approximately 5 million people in the U.S. under the age of 25 are prescribed medications for the treatment of ADHD.

The new research examined two large commercial insurance claims databases on patients ages 13 to 25 years old with ADHD who started taking amphetamines or methylphenidate between 2004 and mid-2015. The sample included more than 220,000 patients.

An analysis showed that 1 out of every 486 patients who started on an amphetamine developed psychosis that required treatment with antipsychotic medication, compared to 1 in 1,046 patients who started on a methylphenidate.

Psychosis is a mental condition characterized by a disconnection from reality. People may experience hallucinations, such as hearing voices in their head, and delusions, including false beliefs like the government is following them or that they're in danger.

"Often, when people develop psychosis, they don't have insight so they don't even realize that they are impaired," Moran explained. "They think these things are really happening. It's very scary."

The findings of the new study, published in the New England Journal of Medicine, are especially concerning, she says, because the use of amphetamine medications in adolescents and young adults has more than tripled in recent years.

"It seems that doctors are choosing to start people on Adderall even though existing guidelines suggest that both stimulants have similar effectiveness," Moran said. "So there needs to be a dialogue between patients and doctors about why they're choosing Adderall over Ritalin-type drugs."

However, for patients already using amphetamines to treat ADHD with no side effects, there appears to be no cause for concern.

"One of the things that's really important about this study is that we only looked at new users," Moran said. "It seemed like risk of this happening happens early on in treatment. Most of the psychotic episodes happened in the first several months of treatment. So I think if you have a child who's taking Adderall or Vyvanse and they've been taking it as prescribed and they're benefitting from it, there's no reason to take them off. This is really something that people should be considering when they're first starting."

It's also more of a concern if an individual is already at an increased risk of psychosis, such as a family history of bipolar disorder or a psychotic disorder. "I might shy away from Adderall in patients with that kind of history," Moran said.

She also notes that medication isn't the only option for treating ADHD. Behavioral therapy, including training for parents, and special accommodations at school can also be beneficial.

However, if symptoms are severe enough, medication may be needed and parents should talk to their pediatricians about the best treatment plan for their child.