He said: “I have mild obsessive compulsive disorder, that’s what doctors call it. That is, I feel like I have to do things in a certain way.
Niall explained he’s had the condition since childhood and left him feeling isolated from his schoolmates.
Today, OCD still affects the musician’s live performances.
He divulged: “I have one fixed sequence. I always have to sing in the same order, move and so on.
“I’ll basically do everything immediately, otherwise I’ll get nervous quickly.”
According to the ‘Slow Hands’ singer, his OCD causes “tics”.