I also think it has to do with all the artificial hormones, chemicals, additives in foods today. Also overuse of vaccines and antibiotics by both children and parents. When we were kids we played in dirt and built up pretty good immune systems naturally, nowadays it seems that parents are keeping everything very sterile and using anti-bacterial soaps and gels may be doing more harm than good.
Kids being labeled as ADD or ADHD is just one more way for greedy pharmaceutical companies to milk the consumer dry with no regard for the people or children, doctors and parents follow along with the program like mindless sheep. All the drugs they give these kids, for no good reason, only make the matter worse with side effects of suicidal or homicidal tendencies.
The vitamins and minerals in our soils are also depleted, so nutrition as taken a downturn...not to mention the GMOs and pesticides, etc. which affect all of our foods and drinks/water today.