Research has shown that people who take stimulants as adult ADHD medication in the form and dosage prescribed do not appear to be at as great a risk for addiction as previously feared. However, when stimulants are abused, the consequences can be extremely dangerous -- even deadly.
According to the National Institute on Drug Abuse, taking high doses of a stimulant can cause an irregular heartbeat, dangerously high body temperatures, and heart failure or lethal seizures.