ADHD really doesn't correlate with IQ, I think what you meant is that adults with ADHD who can get their life together enough to get diagnosed are more likely to also be intelligent, which is true, and those with ADHD and cognitive deficits on top are far more likely to be forgotten and to end up in a prison, which is also sadly true.

I have an IQ of 136, which is considered to be very gifted, but my performance and life success thus far are decidedly average. It's a debilitating condition if it's not detected in time and not managed.