The Harry Potter star developed OCD when he was just five years old, and sought out therapy when his anxiety became so bad that it took him five minutes to switch off a light.
Now the British actor is encouraging anyone with the affliction to turn to a therapist - because the counselling sessions have helped him keep his problem under control.
He tells Britain's Sun on Sunday, ""I had to repeat every sentence I said under my breath. I would encourage everyone to undergo therapy. It doesn't mean you're insane or weak.""
And Radcliffe admits he's in need of another session too: ""I haven't had it this year so far and I'm missing it.""