Cardiovascular safety of methylphenidate among children and young people with attention-deficit/hyperactivity disorder (ADHD): nationwide self controlled case series study

In their article, Shin and colleagues [1] report finding that in the early phase of treatment, methylphenidate (MPH) use in children and adolescents with ADHD was associated with increased risk of arrhythmias and myocardial infarctions.

We are puzzled by the fact that they did not specifically report or incorporate into their discussion the other significant findings listed in Table 2. The most obvious omissions were their findings that children and adolescents who took MPH were at 46% overall reduced risk of heart failure and those who took MPH for more than two months had a 62% lower risk of ischemic stroke. Their oddest non-reported/discussed findings were those listed in Table 4. These include a 473% increased risk of heart failure, a 276% increased risk of arrhythmia, a 200% increased risk of hypertension, and a 555% increased risk of ischemic stroke in the two months prior to starting MPH treatment. The fact that this study yielded such inexplicable and contradictory results casts serious doubt on the authors' claim to have identified a meaningful link between MPH use and cardiovascular disease.

Parents and clinicians should be reassured by the fact that none of the four large population studies have found any evidence of a link between stimulant use and cardiovascular disease in this population [2-5]. Unfortunately, even a single report of a purported link between stimulant therapy and cardiovascular disease, no matter how unconfirmed or unsubstantiated, inevitably looms larger in the public's imagination than the mountain of evidence to the contrary. The authors' announcement of their findings has created quite a stir in the public media and medical press where headlines such as “Ritalin could trigger abnormal heart rhythms and increase heart attack risk” have been frightening both parents and clinicians and will almost certainly lead to many ill-advised decisions to not treat children suffering with ADHD.

Why is this such a big problem? A meta-analysis of 352 studies comparing treated and untreated ADHD found that non-treatment was associated with worse outcome in every category measured -- academic success, antisocial behavior, driving problems, drug use/addictive behavior, obesity, occupational success, services use, self-esteem, and social function [6].

Just as unfortunately, such a “false sighting” of serious risk associated with stimulant treatment of ADHD increases the already substantial stigma that burdens families trying their best to help their children struggling with this illness.

1. Shin et al. Cardiovascular safety of methylphenidate among children and young people with attention-deficit/hyperactivity disorder (ADHD): nationwide self-controlled case series study. BMJ Open, 2016: 353; i2550.
2. Cooper et al. ADHD drugs and serious cardiovascular events in children and young adults. New England Journal of Medicine. 2011. 365: 1896-1904
3. Winterstein et al. Cardiac safety of central nervous system stimulants in children and adolescents with attention deficit/hyperactivity disorder. Pediatrics. 2007. 20 (6) e14940- e1501
4. Olfson et al. Stimulants and cardiovascular events in youths with attention-deficit disorder. Journal of the American Academy of Child and Adolescent Psychiatry. 2012: 51(2): 147-156
5. Schelleman et al. Cardiovascular events and death in children exposed and unexposed to ADHD agents. Pediatrics. 2011; 127:1102-1110.
6. Shaw et al. A systematic review and analysis of long-term outcomes in attention deficit hyperactivity disorder: effects of treatment and non-treatment. BMC Medicine, 2012 10:99.