The long-term use of medication for attention deficit hyperactivity disorder (ADHD) could increase the risk of heart diseases, a study has suggested.

Swedish researchers linked exposure to the likes of high blood pressure and arterial disease, a condition when the blood vessels that carry blood from the heart to the legs narrow.

The team, led by academics from the Karolinska Institutet in Solna, looked at 278,027 people in Sweden aged six to 64 who had an ADHD diagnosis between 2007 and 2020.

Of the group, 10,388 were found to have diagnoses of cardiovascular diseases, including cases of heart failure, arterial disease, arrhythmias and high blood pressure among other issues, and were matched with 51,672 patients without cardiovascular diseases.

Researchers found using ADHD medication for longer was associated with a higher risk of cardiovascular diseases.

Those who had used the drugs had a 9% increased risk for one to two years of use, a 15% higher risk for two to three years, and a 27% higher risk for three to five years. There was a 23% increased risk for more than five years.

The study included all ADHD medications approved in Sweden at the time, including stimulants metylphenidate, amphetamine, dexamphetamine and lisdexamfetamine, as well as non-stimulants atomoxetine and guanfacine.

According to the NHS, there are five types of medicine licensed to treat ADHD in England – methylphenidate, lisdexamfetamine, dexamfetamine, atomoxetine and guanfacine.

These can help relieve the symptoms of the condition, such as difficulty focusing, hyperactivity and impulsiveness.

The main driver of cardiovascular disease was due to high blood pressure and arterial disease, according to the study.

The risk of developing high blood pressure was 72% higher in patients on medication for three to five years and 80% higher for more than five years while cases of arterial disease were 65% more likely after using the drugs for three to five years and 49% more likely after more than five years.

Researchers also found the incidence rate of cardiovascular disease was 7.34 per 1,000 person-years, a measurement that takes into account both the number of people in the study and the amount of time each person spends in the study.

The paper, published in AMA Psychiatry, said the findings “highlight the importance of carefully weighing potential benefits and risks when making treatment decisions about long-term ADHD medication use”.

It added: “Clinicians should regularly and consistently monitor cardiovascular signs and symptoms throughout the course of treatment.”

Henry Shelford, chief executive of ADHD UK, said the study “highlights the need for further research into ADHD – the condition and the treatment options”.

He added: “ADHD is a difficult condition – as we know all too well from the statistics on suicide. Medical decisions hold risk either way.

“There is a risk of doing nothing. There is a risk with the interventions. The more research uncovers, the better choices we can all make, the better monitoring we can make, and the better interventions we can make.”