Most children diagnosed with Attention Deficit Hyperactive Disorder (ADHD) don't outgrow the disorder, as widely thought as a study suggests that it manifests itself in adulthood in different ways and waxes and wanes over a lifetime.

The researchers indicate that decades of research characterise ADHD as a neurobiological disorder typically first detected in childhood that persists into adulthood in approximately 50 per cent of cases. But this study found just 10 per cent of children completely outgrow it.

"It's important for people diagnosed with ADHD to understand that it's normal to have times in your life where things may be more unmanageable and other times when things feel more under control," said lead researcher Margaret Sibley, Associate Professor of Psychiatry and Behavioral Sciences at the University of Washington.

ADHD is characterised by two main clusters of symptoms, according to researchers. The inattentive symptoms look like disorganisation, forgetfulness and having trouble staying on task. Then there are also the hyperactive, impulsive symptoms.

In children, those symptoms look like having a lot of energy, such as running around and climbing on things. In adults, it manifests more as verbal impulsivity, difficulty with decision-making, and not thinking before acting. The disorder affects people differently and looks different depending on what phase of life someone's in.

Some people with ADHD also report a unique ability to hyper-focus. Olympic athletes Michael Phelps and Simone Biles have been open about their ADHD diagnosis.

While many people may experience symptoms similar to ADHD, it is estimated the disorder roughly affects 5 per cent to 10 per cent of the population, the researcher said.

For the study, published in the American Journal of Psychiatry, the team followed a group of 558 children with ADHD for 16 years -- from 8-years old to 25 years old.

The cohort had eight assessments, every two years, to determine whether they had symptoms of ADHD. The researchers also asked their family members and teachers about their symptoms.