The number of children with attention deficit hyperactivity disorder (ADHD) has been rising sharply for about a decade. Currently, of U.S. children have been diagnosed with ADHD. That’s a 42 percent increase in nine years.

There are many theories bouncing around the medical community to try to explain this increase.

One of those has nothing to do with genetics or environment: It simply states that the diagnosis is given too often without the appropriate level of diagnostic inquiry.

But that supposition is false, according to a new study.

Read More: ADHD by the Numbers »

Testing the Theory

The Centers for Disease Control and Prevention’s (CDC) National Center for Health Statistics (NCHS) conducted the 2014 National Survey of the Diagnosis and Treatment of Attention Deficit Hyperactivity Disorder and Tourette Syndrome to gather data about how ADHD is being diagnosed in U.S. children.

Standard best practices dictate that data be used from the Diagnostic and Statistical Manual of Mental Disorders, as well as multiple informants (parents, teachers, etc.) to assess the child’s impairment across multiple environments (home and school) to determine if a child meets the criteria for an ADHD diagnosis.

This is a complex process and it takes time. If diagnoses are being determined quickly or without input of more than just parents, that could signify that kids are being diagnosed with ADHD without a thorough assessment.

The NCHS survey found that hasty, flawed diagnoses are actually not the source of the uptick. The majority of ADHD diagnoses in children were proper, researchers found.

Doctors used rating scales designed to determine the probability of ADHD in 9 out of every 10 ADHD diagnoses.

Three quarters of the children diagnosed when they were 6 years old or older were given neuropsychological tests, and an adult outside the immediate household was consulted in 80 percent of cases.

Read More: How Does Diagnosing ADHD work? »

Parents’ Perspective

Sarah Wayland’s 5-year-old son was evaluated for ADHD and other learning and developmental disabilities.

“His first assessment was done by a neuropsychologist,” explained Wayland, a special needs care navigator at Guiding Exceptional Parents. “It was a three-day test, three hours each day. He completed several tests and parent and teacher descriptions of his behavior were also considered."

The family was also referred to a developmental pediatrician who performed another in-depth evaluation to confirm the ADHD diagnosis and consider other possible conditions.

Some children enter the doctor’s office with obvious signs of ADHD, such as extreme hyperactivity, and receive a quick diagnosis. Sometimes the diagnosis is accurate. Sometimes it’s not.

“[My son] was diagnosed at age 4 by a child psychologist/psychiatrist team,” shared Adrienne Bashista, mother of two boys and founder of nonprofit Families Affected by Fetal Alcohol Spectrum Disorder. “They diagnosed him based on observation and, to be truthful, he ticked all the boxes. He was completely wild, beyond hyper, couldn't pay attention longer than a second.”

Bashista’s son was later diagnosed with fetal alcohol spectrum disorder (FASD) after more in-depth clinical inquiry.

“Many of the symptoms of FASD are exact overlaps of ADHD,” she explained.

Ashley Cotton, a Connecticut mother of three, had a similar speedy ADHD diagnosis experience with her son. While the ADHD diagnosis was accurate in her son’s case, it didn’t explain everything.

“I brought him to the pediatrician who immediately, within moments, decided that [my son] had ADHD,” remembers Cotton. “I was so confused because I thought for sure he just had a hearing or visual issue, or that he may be a bit ‘young’ for his age and would grow in to his own. I left the doctor’s office thinking that it couldn't be true because it was just too fast to diagnose, and just too easy.”

Her son was eventually diagnosed with autism and dyslexia.

Some families experience best practices when evaluating for ADHD but are still uneasy when the diagnosis is delivered quickly.

“I finally convinced [my son’s pediatrician] to test [my son] for ADHD when he was 5,” explained Allison Pulling of Virginia. “We had to do the paperwork for the rating scales and so did his teacher. Then my husband and I went to meet with the doctor. He looked everything over and said he definitely had ADHD and prescribed him medicine. I knew my son had ADHD, so the diagnosis was no surprise, but the quickness of it bothered me a little.”

Pulling sought a second, more thorough evaluation, where the validity of the ADHD diagnosis was confirmed.

A self-described “veteran” parent of a son with ADHD and autism, Penny Williams is the author of two award-winning books on ADHD, “Boy Without Instructions: Surviving the Learning Curve of Parenting a Child with ADHD” and “What to Expect When You're Not Expecting ADHD.” Her third book, “The Insider’s Guide to ADHD: ADHD Adults Reveal the Secret to Parenting Kids with ADHD” will be available in December 2015.