Final answer:
Intermittent Explosive Disorder (IED) is a true personality disorder that involves episodes of extreme anger and can potentially be linked to mass violence.
Step-by-step explanation:
The acronym IED stands for Intermittent Explosive Disorder, which is a behavioral disorder characterized by sudden episodes of unwarranted anger. The statement given is true: IED is indeed considered a relevant personality disorder and may be related to mass killers.
Personality disorders are enduring patterns of behavior that deviate markedly from the expectations of an individual's culture, are stable over time, and lead to distress or impairment. They are not a direct result of substance use or another medical condition.
Intermittent Explosive Disorder relates to the study of personality traits like anger/hostility and how they may correlate with disease or unfavorable health outcomes.
There is also a discussion in the broader field of psychology and neuroscience about how certain personality disorders and mental health issues might intersect with societal issues, such as the accessibility of firearms and the occurrence of mass shootings.