The human brain

Savant syndrome per se is NOT a disorder. Those affected by Savant syndrome generally have a neurological condition such as autism or they have experienced a brain injury. Those ones are the disorders.

I'm kind of fascinated with OCD, but a lot of people overuse the term. If you tend to like things to be neat or straighten a crooked thing, that is not OCD. If you feel like things HAVE to be neat or that you MUST straighten a crooked thing or something bad will happen, then THAT is actual OCD. It is a true disorder that brings a lot of anguish and anxiety to a person suffering from it, and when people exaggerate and claim to have it, it's demeaning to someone who is truly suffering from it.

First of all, you'd need to define what you mean by 'mental disorder'. Do you mean mental illness, learning disabilities, neurodiversity? Many people with 'mental' conditions are intellectually able. I'm quite fascinated by mental health and neurodiversity in general. I know/have known and have worked with people who have personality disorders or autism (at least one person close to me has both). These conditions vary so much, which I find interesting in itself.

I am not well versed with mental health but I believe very many people have mental illnesses unknowlingly