How different mental illnesses are connected to each other

https://www.nature.com/articles/d41586-020-00922-8

Every single mental disorder predisposed the patient to every other mental disorder — no matter how distinct the symptoms. “We knew that comorbidity was important, but we didn’t expect to find associations for all pairs,” says Plana-Ripoll, who is based at Aarhus University in Denmark.

This might be more accurately framed as “Every single mental disorder [diagnosis] predisposed the patient to [being diagnosed with] every other mental disorder.” With that in mind, I can think of a few causes - with relatively minor disorders (like a mild case of ADHD or a person who has autism but is high functioning), a person who has a single disorder might only have a 50% chance of going to get diagnosed, and the same with a second disorder. If they have one, there’s only a 50% chance of getting diagnosed at all, while if they have both, there’s a 75% chance that they get diagnosed with one, and now that they’re already in the office, they will likely get diagnosed with the second. That goes doubly if the person has a minor disorder and a significant disorder (such as schizophrenia) - they’ll definitely go in for the second, but only might go in for the first, but once they’re getting seen for the second, they’ll get diagnosed with the first.

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Huh, this is a really good point. Adam Hunt on twitter also notes:

To explain this link you have to take into account that every mental illness requires a certain level of general dysfunction to meet diagnostic requirements so correlation is inevitable.

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