What's going on with the brain of any particular person is a point in a very high dimension space. What doctors call conditions are regions in that space. The definition of those regions has something to do with understanding and helping the humans and their families, but also something to do with the doctors making money. In the US Healthcare system nothing can be paid for unless it is in service of treating a "condition". Slightly odd that an article in The Economist doesn't mention this.

Related: doctors will refuse to test you to see if what you're suffering from is a particular condition unless that condition actually has a known treatment.