How many people in the world have ADD?

Answer 1

The number of people actually diagnosed with ADD varies wildly from zero percent to 20% in some places in the US. I'm not sure anyone has accurate world statistics on this.

Psychiatrists have been doing studies on ADD or the similar conditions as defined at the time across the world since the 1920's. When you account for differences in the definitions used the range has been remarkable consistent across time and cultures at 3-6%.

Given a world population that is estimated by the US census bureau at just under 7 billion people that would mean that a reasonable estimate is about 200 million to 400 million have ADD world wide. As mentioned above, no where near that many people have been diagnosed and are being treated.