Many people will watch tv, or read something online and say to themselves “oh I must have that disorder.” It is very common amongst first year grad students in psychology as well as medical school students. Of course, this applies even more to the public who have no education in psychology except popular media. The issue is grad students and med students have not yet learned what “differential diagnosis” is. The diagnostic process is much more that what TV or some quick read online, or even an introductory course in abnormal psychology will give you. You may have symptoms that appear to match a given disorder. Now the important issue is do you match the Essential Criterion of the given disorder. However, the real deal is that those symptoms may match several disorders apart from the Essential Criterion. For example, the symptom of trouble sleeping. This is in numerous criteria sets from of course the sleep wake cycle disorders (basically all of them), to anxiety, depression, trauma disorders etc. Therefore, one first off needs to match the Essential Criterion say of depression, then match a certain number of other criteria to actually have the disorder. Most importantly with few exceptions, it must cause clinically, significant impairment in social, work, school, relationships and/or other important areas of life. At first blush it may be easy to see someone acting erratic seemingly talking to someone who is not present, then say they are psychotic, or schizophrenic which is probably the most common thing I hear lay people invoke even medical people. The issue is it could be psychosis (seeing things, hearing things) or it could be, drugs, or coming down from a high or getting high. It could be a person merely talking to no-one yet talks allowed and does not care about how people view them. It could be any number of things.

The point is you do not have nearly enough information of this person passing by to make any judgement at all. What we have learned from diagnostic reasoning which bleeds into lay peoples reasoning is that people operate off of what is called Baye’s Theorem as unfortunately many clinicians fall victim to. It’s a fancy math formula if you look it up online. Yet it boils down to an anecdote you may have heard of. Supposing you live in the U.S. reading this… If you hear hoof steps you will assume horses rather than zebras. The reason is we base gut reaction judgements on Baye’s reasoning or prior probabilities. For example I am 44 years old and never in my life seen a zebra on the street here. I then operate off the assumption that it is most likely a horse. Another example I love to give people is suppose I give you this description: “Shows emotional coldness, detachment, or flattened affectivity,” what would be your initial impression as someone not trained (or even trained)? Over 9 out of 10 people say depression to me. That is a great guess, statistically will be correct more often than not. However, that is word for word the exact criterion 7 of Schizoid Personality Disorder. Most clinicians I pose that question of ask me “what the hell is Schizoid Personality Disorder?” Well the reality is that it is such a rare diagnosis, that most clinicians won’t ever come across the disorder in their career so they are unaware of it.

I live in a city which has decriminalized almost every drug. When I see someone walking around talking to seemingly no one, and no ear bud in, I think they are high on something. If I were living in a city in which all drugs were a criminal offense I won’t consider it as likely, then I will consider psychosis or they are “crazy”. Now invoking the term “likely” is the same thing as saying how probable something is or is not. So, if you live in a city where say cocaine is a criminal offense you are less likely to consider odd, erratic behavior to be a mental issue which is fair statistically. I forget the famous psychologist who said this, but all people are bastard scientists. To an extent all people understand a lot of very basic science they learn up to high school. As a side note. Actually a few years ago I was talking to a medical school student friend of mine. I was going into great detail of a psychological study and the methodology of it. She stopped me and said, Eli you have to realize in medical school we get no further education in scientific methodology than I received in my senior year physics course.

The issue is that when making a diagnosis it takes deep consideration of many different factors and disorders. You cannot just land on one disorder when seeing a symptom that seems characteristic of a given diagnosis. So just because it seems representative of a diagnosis that you have seen on TV, or in the movies does not mean it is that correct disorder. Try to hold off on arm chair diagnoses because it “seems” to fit. It takes years of study and training to do it correctly. You need to see a professional.