In rare cases, children can develop serious cardio-vascular diseases as a side effect of ADHD medicine. In many instances they are no more serious than light chest pains. (Photo: Colourbox)

ADHD medication enhances the risk of heart problems in children

A new Danish study indicates that children recieving ADHD medication have a higher risk of getting heart problems.

The risk of developing heart problems is twice as big for children taking medicine for Attention Deficit-Hyperactivity Disorder (ADHD) when compared to children not receiving the medicine.

The study builds on data from 714,000 children born in 1990-1999. It is the most comprehensive, data-based study within the field explains the head of the project Søren Dalsgaard, a psychiatrist at the National Centre for Register-based Research at Aarhus University.

"I was surprised that the increased risk of heart problems was so high and that the risk did not only apply to children, who were already susceptible to heart ailments," says the psychiatrist.

"The result is worrying. It shows that clinicians must continue to be aware of the risk of heart ailments, when we prescribe medicine to ADHD patients," he says.
The study was published in the scientific publication Journal of Adolescent and Psychopharmacology.

In the study the scientists used a so-called ‘hazard ratio’. The technical term is a measurement of the relative likelihood of an event in two groups over time. A hazard ratio of 1 indicates that the probability of a particular outcome over time is the same in the two groups.

A hazard ratio of 1.83 corresponds to an increased risk of 83 percent. While a hazard ratio of 2.20 corresponds to an increased risk of 120 percent.

(Source: ’Håndbog i sund formidling’ by Siff Malue Nielsen and Ole Nørgaard, 2014).

The connection between medication and the risk of heart ailments

In the study, psychiatrist Dalsgaard first found a risk estimate for the difference between children without ADHD and children with this diagnosis.

The study showed that when children were given ADHD medicine their risk of getting heart problems rose from approximately 0.5 percent to about 1 percent. The precise increase of risk was calculated to be 83 per cent. 

Søren Dalsgaard stresses that this risk is still relatively low, also for the group receiving ADHD medicine. 

In-depth study of medication

The study covered nearly all types of ADHD medicine. Methylphenidate-based medications account for 98 per cent of treatments. This group of medication is sold under the brands Concerta, Methylin, Ritalin, Equasym XL, Motiron and Medikinet.

Other medicines such as Strattera account for the remaining 2 per cent of treatments, but their use is so low that Søren Dalsgaard did not have enough data to assess the precise effects of non-methylphenidate medications. Nonetheless, they were included in the study.

Earlier studies have shown that adults do not have a greater risk of cardio-vascular diseases or strokes if they take ADHD medicine.
Other studies on grown-ups have shown varying results.
(Source: Søren Dalsgaard and

To make sure that the measured difference was not due to the disorder itself, the scientists compared children with ADHD diagnosis, who were receiving medicine, with other ADHD diagnosed children, who were not receiving medicine.

The scientists found, that the hazard ratio for children receiving ADHD medicine was 120 per cent higher, than children not getting medicine.

Information from cardiac departments

The information about cardio-vascular problems in children receiving ADHD medicine comes from cardiac departments at Danish hospitals, where the children are controlled and kept for observation in case of suspected problems.

Of the children with heart ailments, 54 percent were diagnosed with 'unspecified heart or cardio-vascular disease'. This could for example mean a too high pulse or  heavy heart beating. 23 percent were diagnosed with arrhythmia, while 8 percent were diagnosed with elevated blood pressure.

Numbers show that risk is connected to changes in dose

Another result was that when changing the dose of Ritalin from high to low the numbers showed, that the risk of heart problems grew.

"That there could be a risk involved in lowering the dose was a great surprise," says Søren Dalsgaard and continues:

Søren Dalsgaard's study is the equivalent of 6,767,982 years of observation, "the period we have followed the subjects, has been much longer than in any other previous studies (up to eight years)." (Source: Søren Dalsgaard)

"But this is something that needs further studies, before we can be completely sure about the result." 

He explains that the correlation between the two factors could be caused by a reduction in the dose prescribed, because the GP has noticed indications of cardio-vascular problems.

Uncertainty concerning the meaning of 'unspecified heart diseases


Tine Houmann is a psychiatric medical consultant at the Children and Adolescent Mental Health Centre in Glostrup, Copenhagen. She regards the study to be interesting and robust, because it relies on a large amount of data. But she remains unconvinced by results connected to 'unspecified heart or cardio-vascular disease'.

"What 'unspecified heart or cardio-vascular disease' actually means is a little unclear," she says. "Does it mean children who have gone for a control check, because they perhaps felt chest pains, without there actually being a problem - or did the doctors find a problem?"

Tine Houmann explains that American studies have shown that children taking ADHD medicine, go to the Emergency room more frequently than other children. This is probably, because doctors and parents are more aware of the medication's side effects.

Søren Dalsgaard agrees with Tine Houmann, that 'unspecified heart or cardio-vascular disease' is unclear.

"But it does not just mean, that they have had symptoms. By itself, that is not sufficient to get a diagnosis," says Søren Dalsgaard. "The register includes diagnoses such as 'examined for heart ailments, nothing found'. We haven't included these diagnoses, but they would be diagnoses given to children, who were examined, but where there was nothing wrong with them."

Psychiatrist: Medicine can be better than nothing

Tine Houmann emphasises that doctors and parents should not be scared of results like those published in the study.

"It is important that we do not become so afraid of rare side effects that we do not give medicine to children with ADHD. Because the problems and risks connected to unmedicated ADHD are severe. It can lead to addiction, crime and developing psychiatric diseases," says psychiatrist Houmann and continues:

"If the patient has moderate to severe ADHD, medical treatment can be very beneficial to the patient's quality of life, basic activities such as going to school and having normal relationships with friends and family." 

But although heart ailments are rare side effects of Ritalin, they can be serious. According to Tine Houmann, it is vital that children, who receive ADHD medicine, have control check-ups every six months.

No reason to prescribe less medicine

Søren Dalsgaard believes that his study confirms that doctors must think twice when prescribing ADHD medicine.

He does not think that his study should or will result in doctors prescribing less medicine to children with ADHD, as Danish doctors already prescribe medicine to far fewer children with ADHD compared with doctors in other European countries and the USA.

Two per cent of Danish children are diagnosed with ADHD, and only two-thirds of them are given medicine to treat the disorder.
Read the original article in Danish on

Translated by: Louisa Field

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