Bullshit. Some diseases are real with an identifiable, physical cause. Others, like ADD, are mostly disease mongering for profit. ADD used to be a kid thing, but in the recent past an explosion of "adult ADD" advertisements swept the scene, taking advantage of adults with stressful lives and making them think it was caused by a disorder. These people aren't disordered, they just have stressful lives as they try to make it in a fast paced, high demand world which they simply aren't cut out for.
If you were to increase the demands on the public by two fold, you would have millions more people who suddenly wouldn't be able to cope, and the drug industry would come out with a cure for them, guaranteed. After all, if they aren't happy and living a good life, something must be wrong with them.