According to the Brown University Child and Adolescent Psychopharmacology Update, Volume 17, Number 2 February 2015 issue, children with ADHD are likely to have co-occuring irritability (marked by temper outbursts and anger) between 25%-45% of the time.  In addition, research has also shown that irritability predicts depression and anxiety.
    Russell Barkley in his book Attention-Deficit Hyperactivity Disorder 4th edition, notes that the inability to inhibit frustration, impatience, anger and hostility are common in individuals with ADHD.  In addition, the more the severe the symptoms are (especially hyperactivity and impulsivity) the more severe the frustration, temper and anger.  Longitudinal research has also shown that maternal ratings of childhood irritability during early childhood are predictive of later ratings of severity of ADHD symptoms.    Barkley also cites ample research that severity of ADHD symptoms negatively impacts peer relations,  there are elevated rates of road rage, higher risk for arrest rates and occupational performance problems. Research has shown however, that medication designed to manage the symptoms of ADHD positively impacts the effective management of emotions.