From the time he was a baby, Max, now 7, struggled with crippling anxiety.

"He would fly into screaming rages for no apparent reason," says his mother, Stacy, a 44-year-old lawyer from Seattle who wanted to keep her family's identity private. "He was constantly on edge."

At 2 years old, Max began three years of behavioral therapy, "but it did nothing to help him," Stacy says. His fear-driven outbursts continued into kindergarten. "Some days, he couldn't even walk into class. I'd have 45 minutes of crying and screaming."

Finally, at age 5, Max went on the antidepressant Prozac and his fear quickly subsided. "Prozac almost immediately brought our joyful, loving son back to us from his previous perennial fight-or-flight existence. He's his best self every day," says Stacy, whose only question is why she had resisted the medication for so long.

A surprising number of the nation's youngest children are being prescribed psychiatric drugs, some younger than preschool, according to health-care industry data on physician prescriptions in the United States.

Widely reported data collected in 2014 from IMS Health show that more than eight million children are prescribed drugs for anxiety, depression, attention-deficit/hyperactivity disorder (ADHD), and bipolar and behavioral disorders. More than one million of them are younger than 5.

But rigorous studies of these drugs in young children is "incredibly poor," says Mary Margaret Gleason, a pediatric psychiatrist at Tulane University. "We don't know much, especially with preschoolers," she says. "The older kids get, their brains have already developed, and we have more information."

The National Institutes of Health confirm that the use of antidepressants has "risen dramatically" since the 1990s. Anxiety is the most common type of mental-health disorder in children, according to the American Academy of Pediatrics. About 10 percent of all young children deal with generalized anxiety, panic, separation anxiety, and phobias.

These disorders often go hand-in-hand with ADHD and depression. Symptoms can include fears about daily life, headaches and stomachaches, trouble concentrating or sleeping, and fear of social situations.

Studies on the safety and effectiveness of psychotropic drugs in young children are "limited," according to the AAP, and only two studies have been conducted, both on children 7 and up.

A review of pediatric trials between 1988 and 2006 suggests the benefits of medication outweigh the risks in children with depression and anxiety disorders, according to the Centers for Disease Control and Prevention (CDC). But at the same time, the CDC has shown increasing concern about off-label prescriptions for drugs to treat ADHD. An estimated 11 percent of all 4- to 17-year-olds have been diagnosed with the disorder, and that number continues to grow.

Some parents say they feel pressured by teachers and pediatricians to medicate for what they see as behavioral, not mental-health, problems.

Kirk Jennings Jr., an electrician from Prince George's County, Maryland, says his son Jay was diagnosed with ADHD at the age of 5, after his kindergarten teachers voiced "concerns" about disruptive behavior.

"At times he was a little loud and little too playful, but he's still on the honor roll," says Jennings, 37. "It seems teachers are now a little less tolerant."

A therapist suggested home therapies could help Jay's behavior, and his mother, who is separated from Jennings, agreed to medicate their son. Jennings disagreed.

Jay, now 10, has been on a list of "constantly changing" medications to stabilize his mood, with side effects such as dry eyes, irritable skin, fidgeting, nail-biting, and heightened fear.

Jennings says Jay's behavior is "typical" for boys his age, and his parents' separation triggered anxiety. "My biggest worry is the medication, which makes him a lot more calm, but is hindering his ability to cope. He is never truly learning how to behave."

About one in five children will be diagnosed with a mental illness before the age of 17, according to the National Association for Mental Illness. But not all of the children will be treated.

For years, Heidi Walker of Kingwood, Texas, wasn't able to get treatment for her 9-year-old son, Roanin, who now takes multiple drugs for ADHD, generalized anxiety, and severe sensory deficit. Walker says she was "totally against" medication when Roanin was first diagnosed at 2. But by kindergarten, his behavior was out of control.

"He would run out of the classroom," says Walker, 37. "He got overwhelmed because of sensory issues in a group of people. If someone got too close, he'd attack them."

At home, he never slept and acted impulsively, sometimes dangerously (he once took a knife to the television set). One time, Roanin became so angry, he peed on his brother's pillow and filled his guitar with water from the toilet.

"We tried a diet change and that wasn't working," Walker says. "He was in therapy. We tried everything."

When Roanin was 5, doctors prescribed a stimulant for violent outbursts. But there were side effects. The first drug made his aggression worse; another, too sleepy.

"It's a double-edged sword," Walker says. "I hate to medicate him, but if I don't, he is more miserable, and so is everyone else in our house. He also tells me he feels off when he's not taking his meds."

Walker says she tries not to judge others for using medication. "Having dealt with this, it's a personal choice," she says.

But sometimes, doctors are too quick to prescribe before looking for physical causes, says Laura (not her real name), a 49-year-old from San Francisco. Her daughter was put on Prozac for anxiety and obsessive-compulsive symptoms. Since preschool, she's had stomachaches, tantrums, and insomnia. By 11, she was talking about suicide.

"It was really a puzzle," Laura says. "We saw a family therapist and that didn't help."

After seeing multiple specialists, Laura's daughter was diagnosed with celiac disease, an autoimmune condition that causes malnutrition and, in rare cases, psychiatric symptoms. Since removing gluten from her diet, the girl is off medication and her anxiety has improved, her mother says.

"I am not against medication in general," Laura says. "It's not a choice anyone makes lightly."

For disruptive behavior and anxiety disorders, the first line of treatment should always be psychotherapy, which has more lasting effects than medication, says Gleason, the Tulane psychiatrist. "Mental-health issues in young children occur usually in the context of relationships, and we have treatments that are effective to help children build those relationships," she says.

But, at the same time, these disorders in preschoolers often go untreated, because of lack of coordination between pediatricians and psychiatrists, social stigma, and insurance that typically only covers short-term treatment.

"There are adverse effects when untreated anxiety doesn't allow a child to participate in school or social activities," Gleason says. "We start with cognitive behavior therapy and if it's not effective, we weigh medication."

Such was the case with Stacy's son Max, a gifted child whose anxiety was intractable, according to his therapists. When asked by his parents about taking medication, Max said he was eager to try anything that would make his constant terror "go away."

"There is a strong societal bias away from medicating and an insistence it's drugging your child and that they simply need to learn to cope," Stacy says. "Why are we asking our youngest people, who don't have the skills to cope and who are flooded with emotions, to deal with what adults have decided they can't handle?"

Gleason says the medical community paradoxically continues to be in both "over-treatment and under-treatment mode" when it comes to mental disorders in children.

"As with all medications, there is a hope and a wish that there is an easy fix that doesn't have side effects," she says. "At the same time, we want to avoid giving children unstudied and untested medications. There are a lot of ripple effects."

This story originally appeared as Prozac preschool on Pacific Standard, an editorial partner site. Subscribe to the magazine's newsletter and follow Pacific Standard on Twitter to support journalism in the public interest.