I don't think "ADHD" existed when

I was a child. There were children who were "fidgety" and who "didn't listen" and "didn't concentrate" but the Attention Deficit Hyperactivity Disorder label wasn't something people knew about.
Now we are being told that it is a serious disorder which requires the administration of medication to calm children down, sometimes to children as young as two. Indeed without such medication your "disruptive" child might not be permitted to attend a day-care centre.
I am not a medical person and I most certainly couldn't diagnose something like ADHD but I wonder why it has become an issue.
Is it a physical condition or is it a problem associated with the sort of life style we now lead?
My mother worked as a teacher. I knew other mothers who worked too. They worked in shops, banks, hospitals, and offices. Not all mothers worked outside the home but an increasing number did. Most however did not work until all their children were of school going age. If they did work then children were usually cared for by grandparents. Before my mother went back teaching full-time she would do the occasional "relief" day and my paternal grandmother would care for my two small sisters. She would come to our home, about a mile away, and care for them there. "Day Care" as such simply didn't exist.  There was "Kindergarten" but it wasn't seen as a child minding service for working parents. 
Most children played at home and they often played alone outside in everything but wet weather. Most children, even the poorest, had tricycles or pedal cars. They might be third or fourth or fifth hand even - certainly ours were - but they were toys which encouraged us to be active. We "dressed up" in old clothes belonging to our parents and pretended to be pirates, cowboys, space men and all sorts of other things. We played imaginative games. My siblings climbed trees. Even I managed to scramble up a precarious heap to sit on the lowest branch of a tree. It was well below the height of the back fence so it must have been much less than two metres high but it was still "high" to me. 
Our mothers didn't supervise our outdoor play. They didn't provide us with a stream of electronic entertainment. I don't suppose everyone had a "bedtime" story either. We certainly didn't have a huge quantity of plastic toys relating to films like "Frozen".  My father had made me a dolls house, a replica of our house in the little country town where I was born. The furniture was simple. There were no dolls in it. I used it mostly as a "railway station" for my Hornby clockwork train set with the green engine and the simple track that travelled the world from the time I was three.  I never quite forgave my mother for giving it away when we moved. 
I think we played quite differently. We would come inside reluctantly. We were dirty and tired and hungry. 
While we were outside  unsupervised our mothers, particularly our working mothers, were getting on with other things. They were doing much of it without the modern conveniences. They had to make our clothes because you couldn't just head to the nearest shopping centre and buy them. You had to actually polish the floor when you cleaned it. 
When we went to school we didn't have "before" and "after" school care or a supervised activity every afternoon. We went home. We went outside and we played.
I could be completely wrong but I can't help wondering whether this epidemic of ADHD isn't related to the modern lifestyle where there is constant supervision and the overuse of a range of electronic baby sitters.