The links between mental disorders
There&#x27;s a couple related shared factors that cause correlation between diagnosis of various mental disorders.<p>1. People who are doing okay don&#x27;t seek out diagnosis. One big example is Bill Gross, the &quot;Bond King&quot; who manages mutual funds - he happened to read the description of Asperger&#x27;s and realize he had it <i>in his seventies</i>. Psychologists do not see a representative sample of society. If diagnosis A and B are both mild enough to cause some people with it to not seek treatment, but everyone with <i>both</i> to do so, you&#x27;ll see a correlation between A and B.<p>2. All mental health diagnostic criteria share a clause that sounds like &quot;and these symptoms cause a significant amount of distress or ill-functioning to the patient.&quot; This is similar to the first factor, but happens after people seek treatment; if you tell a psychologist that you aren&#x27;t having <i>any</i> problems in your life, they do not diagnose you with depression, anxiety, ADHD, etc. It almost doesn&#x27;t matter what you have going on, if it doesn&#x27;t cause problems its not worth using medical care on, so it doesn&#x27;t get diagnosed. And again, if you only have one kind of thing causing you problems, it&#x27;s more likely to not be severe enough to warrant some kind of diagnosis.<p>3. Similar to the previous factor, mental health diagnoses are used to gatekeep medical care and social support. So, people who need more resources than they currently have are going to push more for additional mental health diagnoses, while people who are more okay are going to be fine with the first one proffered. Eg, a young woman who is extremely anxious and whose mom yells at her all the time goes in, gets diagnosed with anxiety and prescribed anxiolytics, things are still bad because her mom keeps yelling, so she goes back and gets a depression diagnosis and anti-depressants. Or a school can offer accommodations for ADHD and not autism, or vice versa, so someone with one goes back and asks the psychologist for the other.<p>In short, there&#x27;s a general willingness-to-seek-diagnosis that&#x27;s an <i>obvious</i> latent variable for mental health diagnoses. I&#x27;d be more surprised to <i>not</i> find a positive correlation between two arbitrarily picked mental health diagnoses. If there&#x27;s an outright negative correlation, that&#x27;s something that would be actually indicative of a biological link of some sort - either the biochemistry of one complex protects against the other, or they&#x27;re a pair of under&#x2F;over-activity of a system, or the like.