ADHD Drugs and Serious Cardiovascular Events in Children and Young Adults — NEJM

In conclusion, in our study involving children and young adults with 2.5 million person-years of follow-up, there were 3.1 serious cardiovascular events per 100,000 person-years. Although the point estimates of the relative risks for ADHD drugs did not indicate increased risk, the upper limit of the 95% confidence interval suggested that a doubling in the risk could not be ruled out. However, the absolute magnitude of any increased risk would be low.

The entire article is worth reading given the potential serious side effects of the drugs in question.