When it causes you or the people around you an unusual level of suffering.

"Unusual" would be defined as a persistent negative state uncommon amongst your peers of similar social/economic level.

Having an argument with your mother because you don't want to clean your room is a fairly common emotional battle between parents and teenagers.

Having an argument every day to the point where someone is in tears and relationships get strained to the point where you're seriously questioning how welcome you are in your own home, that's an unusual level of suffering.

"Neurodiversity" preaches acceptance of people who don't fit within the regular expected mould for human behaviour.

I'd say it's a pretty good litmus test to use your own sense of morality or personal well being to decide who you would let into your life.

Do you want to accept the guy who's a little quiet and prefers to watch a movie together in silence than have a long conversation?

Do you want to accept the habitual drug user who steals from his family and can't control his anger around vulnerable people?