There is no direct causality associated between ADHD and suicidal behaviors. A detailed medical study compared outcomes and limited the analyses to ADHD patients who had received some sort of medication treatment and then compared suicidal risk with periods of no medication treatment for their condition.
This analysis found no increased risk for suicide from non-stimulant medications. More importantly, researchers concluded from their study that patients treated with stimulants actually had a lower risk of suicide than when they were not treated for their condition.
This protective effect of stimulant medication provides further evidence of the long-term effects of stimulant medications which have also been shown to lower the risks for traffic accidents, criminality, smoking, and other substance use disorders.