People with attention deficit hyperactivity disorder (ADHD) are twice as likely to die prematurely than people without the condition, with accidents the main cause of death, a new study has found.

Danish researchers followed the progress of almost two million people, including over 32,000 with ADHD, from their first birthday to 2013. In 2013, the oldest of the participants were 32 years old.

The study compared the causes of premature death in those with the condition and those without.
ADHD is a neurodevelopmental disorder, the main symptoms of which include inattention, impulsivity and hyperactivity. Those affected show poor concentration, are often unable to complete tasks, day dream a lot, are distracted easily, act without thinking and can suffer temper tantrums.

Hyperactive symptoms can include restlessness and not being able to remain seated, such as during meals. In adults, this can manifest itself through excessive talking and feelings of being overwhelmed.

The study found that people with ADHD have a lower life expectancy than those without it. In fact, they were twice as likely to die prematurely compared to people without the condition. This was the case even when known risk factors were taken into consideration, such as age, gender and family history of mental health problems.

The researchers noted that this increased risk of death was mainly due to unnatural causes. Over half of the deaths were due to accidents.

They also noted that this risk of dying prematurely increased with the age at diagnosis. In other words, the older a person was when they were diagnosed, the higher the risk of a premature death.

For example, if a child was diagnosed at the age of six, they had twice the risk of dying prematurely compared to those without the condition. However, if a person was not diagnosed until the age of 18, they were at least four times more likely to die prematurely compared to those without the condition.

The study also found that females with ADHD appeared to be more at risk of premature death than males with the condition.

Previous research has found that people with ADHD are at an increased risk of having other disorders, such as substance abuse disorders and conduct disorder.

"Our findings emphasise the importance of diagnosing ADHD early, especially in girls and women, and treating any co-existing antisocial and substance use disorders. It is however important to emphasise that although the relative risk of premature death is increased in ADHD, the absolute risk is low," the researchers from Aarhus University said.

Details of these findings are published in the journal, The Lancet.