I’ve been invited to speak to a group of attorneys who work at the interface of psychiatry and the law. The topic of my talk? “Psychiatry 101.”

A psychiatrist who gave this talk to a similar group a few years ago advised me: “You should assume that lawyers are laymen. It’s surprising how little they know, given the work that they do.”

This teaching opportunity to teach has given me pause: What is mental illness?

Most of my work has been with people with few resources (no home, no job, etc.) or with people who are experiencing symptoms that cause significant distress (they won’t eat because they think all food is composed of their internal organs; they often try to kill themselves due to hearing voices telling them to do so; etc.). Most people would agree that these individuals have “mental illnesses”, whether “caused” by their circumstances (imagine people trying to set you on fire or rape you because you are sleeping outside) or by apparent biological events (imagine a freshman in college with an unremarkable history who, over the course of months, begins to believe that the government inserted a chip into his brain).

I have also worked in settings where:

• a wealthy man’s wife felt overwhelmed with anxiety about which of their three homes they should remodel first
• a aerospace engineer with no symptoms wanted to try an antidepressant because his girlfriend started taking one, and she now seemed to have greater clarity of mind; “maybe that will happen to me, too”
• a college student felt depressed because his parents wanted him to pursue a professional degree, but he didn’t want to do that

Do those individuals have mental illnesses? Does psychological suffering equate to mental illness? Even if they are able to get on with the necessary details and difficulties of life? (1)

My mind then spins to recent events, such as the Germanwings place crash. Many people have argued that, because the co-pilot killed people, he was mentally ill. He apparently had a diagnosis of depression, but I agree with Dr. Anne Skomorowsky that a diagnosis of depression alone does not explain why he committed mass murder.

But if he was mentally ill, what diagnosis would best describe his condition? What do we call it when people kill other people? Is that behavior alone sufficient to say that someone is mentally ill? If so, what do we make of:

• soldiers killing other people during war
• gang members who, without provocation, shoot police officers or other gang members
• suicide bombers
• parents who kill their newborn infants because the babies aren’t the parents’ desired sex

Does a person’s intentions affect the definition of “mental illness”? (How good are we at reading the minds of others? We often assume intention when observing behavior. And those assumptions can be way off.) Does the situational context also affect what a “mental illness” is? (When in Rome, do you do as the Romans do? What if you don’t know what Romans do?)

People have surmised that people who kill other people may have conditions such as antisocial or narcissistic personality disorder. However, these designations are still problematic: Not everyone with those personality disorders kill people.

Perhaps this is why I prefer to work with people who demonstrate behaviors that undoubtedly impair their function. (2) I am reluctant to describe most people as “mentally ill” because some behaviors that people find bizarre have helped the person cope with their circumstances. The people who always wear masks or scream on the street? Those behaviors may have somehow protected them in the past — even if it means that the general public derides them for being “weird”. It seems unfair to say someone is “ill” when what they have done before in the past has given them some degree of protection. (To be clear, I don’t necessarily apply this formulation to people who have committed murder. For example, I can’t think of how flying a plane into a mountain could ever be an adaptive coping skill.)

Words matter. I’m not sure that I have more clarity yet about what I should teach, though it is clear that I should focus on how I phrase the information I present.

1. Do not misunderstand: People with means can and do have mental illnesses. Take the software developer who was certain that public surfaces were contaminated with exotic diseases; he couldn’t get himself to go to work or spend time with friends due to fears that he would get sick and die. Or the accountant who, if she doesn’t sleep enough, would believe that she is the mother of God; she went to hospitals insisting that she was in labor with Jesus when, in fact, she was not pregnant.

2. It is easier for me to work with people who demonstrate clear evidence of “impairment in function”. Part of this is due to the greater ease and clarity in diagnosis: If someone’s symptoms are within the spectrum of normal human experience, then diagnosis is unnecessary. Part of this is also due to treatment: Some interventions in psychiatry — specifically medications — are not benign. Furthermore, it is unclear how some — many? — psychotropic medications work. We first must do no harm.

Maria Yang is a psychiatrist who blogs at her self-titled site, Maria Yang, MD.