
Though over three years have passed since the start of the pandemic, we on Earth have yet to escape the specters of death and destruction. With murderous tragedies large and small happening around the globe, one might wonder, “All these people who are killing other people: There must be something wrong with them. Do they have a mental disorder?”
The Diagnostic and Statistical Manual, now in its fifth, text-revised edition, provides this definition for “mental disorder” (emphases mine):
A mental disorder is a syndrome characterized by clinically significant disturbance in an individual’s cognition, emotion regulation, or behavior that reflects a dysfunction in the psychological, biological, or developmental processes underlying mental functioning. Mental disorders are usually associated with significant distress or disability in social, occupational, or other important activities. An expectable or culturally approved response to a common stressor or loss, such as the death of a loved one, is not a mental disorder. Socially deviant behavior (e.g., political, religious, or sexual) and conflicts that are primarily between the individual and society are not mental disorders unless the deviance or conflict results from a dysfunction in the individual, as described above.
Let’s consider some examples:
The man who shot 18 people in Maine. There are accounts that he has heard voices in the recent past. It is unclear if these voices were related to his threats to carry out a shooting at a military base. Reporting suggests that these two events resulted in a psychiatric hospitalization.
If we assume that he is still experiencing now the symptoms he had over the summer, he has a disturbance in his cognition (hearing voices) and behavior (use of a firearm to kill other people). We don’t know if the voices have caused him distress. He is certainly experiencing major disability at this time, as it seems that he has no social connections at this moment and he isn’t able to engage in activities such as work and leisure. He has demonstrated socially deviant behavior that, at least the way it is reported, is related to a dysfunction inherent to him.
Thus, it seems likely that this man who has killed 18 people in Maine has a mental disorder.
The Long Island Sex Killer. This is the man who allegedly killed 11 women between 1996 and 2011 and put their remains on Gilgo Beach. This man worked as an architect in New York City, was married, and had children.
It is debatable if he had a clinically significant disturbance in his thoughts, emotions, and behaviors: No one in his life seemed to notice any disturbances. For 15 years he presumably didn’t exhibit concerning distress or disability, as he was able to maintain multiple roles in his life with success. No one knew of his socially deviant behavior until he was caught.
Under this framework and given what has been shared, the Long Island Sex Killer does not appear to have a mental disorder.
People fighting in wars. This can include a military attacking an opposing nation-state, an organization attacking a nation-state, or a nation-state attacking an exclave.
We’ve already encountered a barrier: Mental disorders, by definition, only occur in individuals, not populations.
So let’s broadly consider the leadership of these populations, such as elected officials and others with high rank and authority. Propaganda obscures whether any of them are exhibiting disturbances. Note that their followers would not interpret their leaders’ thoughts, emotions, and behaviors as disturbed. Any distress the leaders express is related to their rage towards the enemy. Anyone showing disability would likely be removed, as this would be construed as a vulnerability. Attacking the enemy is not socially deviant behavior. (Resisting such efforts is.)
Leaders who order the killing of other people, in this framework, do not have mental disorders.
(As you already know, those fighting and harmed in wars are at higher risk of developing mental disorders. It is unjust that once someone demonstrates disturbances, distress, and disability due to war, the consequences of a state action land solely on individuals who must bear the psychological burdens and stigma.)
So, if mental disorders are not the underlying reason why people kill other people, then what is?
(Evil?)
(If it is evil, that is not something psychiatrists can treat.)

