Are mass shooters mentally ill?

President Trump says yes, many in the mental health community say no.

Mental illness is commonly defined as an impairment that interferes with one’s ability to make decisions based on evidence. An obvious example is delusions of imaginary worlds that do not exist. A mentally ill person says that there is a monster in the closet but the average person can look in the closet and not see the monster.

But what about ideology? Strong views on an issue can cloud people’s perception of the facts. But what about a value system that values some evidence more than others? Are there bad values that a person can have? Mental health professionals generally try to avoid such topics because they don’t want to seen as picking sides in a political debate.

A person is generally viewed as not mentally ill if they take a course of action after analyzing the pros and cons of action. Even an action that could lead to certain death or a lifetime of incarceration might be worthwhile to a suicide bomber, who sees their death as a way to get to heaven. They may have fully understood the consequences of their actions and made a rational decision based on their ideology – and therefore are not mentally ill.