Health Secretary Robert F. Kennedy Jr. has often criticized prescription stimulants, such as Adderall, that are primarily used to treat attention deficit hyperactivity disorder.

“We have damaged this entire generation,” he said last year during a podcast, referring to the number of children taking psychiatric medications. “We have poisoned them.”

In February, the “Make America Healthy Again” commission, led by Mr. Kennedy, announced plans to evaluate the “threat” posed by drugs like prescription stimulants.

But are they a threat? And if so, to whom?

Like many medications, prescription stimulants have potential side effects, and there are people who misuse them. Yet these drugs are also considered some of the most effective and well-researched treatments that psychiatry has to offer, said Dr. Jeffrey H. Newcorn, the director of the Division of A.D.H.D. and Learning Disorders at the Icahn School of Medicine at Mount Sinai in New York.

Here are some answers to common questions and concerns about stimulants.

What are prescription stimulants?

Prescription stimulants are drugs that help change the way the brain works by increasing the communication among neurons.

They are divided into two classes: methylphenidates (like Ritalin, Focalin and Concerta) and amphetamines (like Vyvanse and Adderall).

The drugs are most often prescribed to treat A.D.H.D., but they’re also used for conditions like narcolepsy or a binge eating disorder. Sometimes they are also used off-label, for treatment-resistant depression, or catatonia, a syndrome that can cause a patient to move in unusual ways, become immobile or stop talking.

The medications work by amplifying the activity of the neurotransmitters dopamine and norepinephrine in the nerve cells of the brain. Dopamine plays a role in creating the desire for something and the motivation to get it, while norepinephrine can increase alertness and make it easier to focus.

People with A.D.H.D. may have a deficit of both of these chemicals, so when they use stimulants it essentially helps “even them out,” said Dr. Anthony L. Rostain, chairman of the department of Psychiatry and Behavioral Health at Cooper University Health Care, which is based in Camden, N.J.

For some users, the effects are profound. “It’s like glasses for poor vision,” Dr. Rostain said.

Are stimulants always used to treat A.D.H.D.?

No.

Not everyone who has been diagnosed with A.D.H.D. takes stimulants. There are also non-stimulant medications, like Strattera (atomoxetine). And some people don’t require any medication at all.

Other interventions, such as behavioral therapy, parent training, school supports, and lifestyle changes to regulate sleep and exercise, are important — regardless of whether someone needs medication or not.

How many people are taking them?

The use of prescription stimulants has been on the rise since 2012, particularly among adults, and has sharply increased in recent years among women as well as patients ages 20 to 39.

In 2023, an estimated 6 percent of adults had a current diagnosis of A.D.H.D. and about one-third of those patients reported taking prescription stimulant medication, according to an analysis from the Centers for Disease Control and Prevention.

In children and adolescents, however, the number of stimulant prescriptions has been more stable in recent decades.

Overall, it is estimated that about 5 percent of children in the U.S. are currently prescribed medication for A.D.H.D. (Not 15 percent, the number stated by Mr. Kennedy during his confirmation hearing in January.)

A study published in February found that prescriptions actually declined among children after the pandemic began.

How often are prescription stimulants misused?

Government drug use surveys show that in 2022, among people 12 and older, 1.5 percent reported misusing prescription stimulants in the past year — taking the drugs without a doctor telling them to do so, or not in the manner they were prescribed. Sometimes people are aspiring to be more productive or to stay awake, but the drugs are also used recreationally, and can produce a high by swallowing, smoking or snorting the medication — or injecting it into the bloodstream.

Young adults ages 18 to 25 had the highest rates of misuse: 3.7 percent.

Among adolescents 12 to 17, the percentage of misuse was much smaller: 0.9 percent.

This number can vary depending on where they live: In some U.S. schools, as many as 1 in 4 high school students report misusing prescription stimulants, often motivated by their desire to perform better in school. Some schools report no issue with stimulant misuse.

What are the potential side effects?

Taking stimulants can cause elevated blood pressure and heart rate, a reduced appetite, difficulty sleeping, and restlessness or agitation.

Other common side effects include headaches, an increase in body temperature and abdominal pain.

Less frequently, stimulants have been known to temporarily slow a child’s growth, Dr. Rostain said, which is why they should have their height and weight monitored by a medical provider while they’re taking the drugs.

There is also a small risk of developing psychosis that may be tied to dosage. And when stimulants are misused, they can be addictive.

Patients and their doctors have to weigh the benefits of taking stimulants against these risks. A.D.H.D., particularly when left untreated, is associated with reckless behaviors like careless driving, unsafe sex, substance abuse and aggression. A recent study showed that people with the diagnosis are, on average, dying earlier than their peers — about seven years earlier for men, and about nine for women.

How long should stimulants be used?

It depends.

Studies have shown that A.D.H.D. symptoms can change over time, improving and then worsening again, or vice versa. “It’s not consistent,” Dr. Rostain said. “They wax and wane for many people.”

As a result, he added, people may end up using A.D.H.D. medications intermittently.

Still, some people take these drugs longer term, said Dr. Lenard A. Adler, the director of NYU Langone Health’s Adult A.D.H.D. Program.

“That being said, it’s always appropriate when someone is stable on psychostimulants to attempt to lower the dose,” Dr. Adler added.

If a patient continues to do well, he said, then it’s worth exploring whether the medication is still needed.

Is there still a medication shortage?

Yes.

The stimulant shortage that began in 2022 continues. According to the Food and Drug Administration, as of March, methylphenidate hydrochloride extended release tablets and patches, as well as other types of amphetamine tablets, are either unavailable or in short supply.

The availability of specific drugs and formulations can vary by region, Dr. Rostain said.

“It leads to a lot of uncertainty, unpredictability and a lot of anxiety on the part of patients,” he added.