It was present 20 / 30 years ago.
Ritalin has been used since the 1960s:
By 1966 the `experts' had come up with a definition of the sort of child for whom Ritalin could useful be prescribed. Children suffering from Minimal Brain Dysfunction (MBD), the first syndrome for which Ritalin was recommended, were defined as `children of near average, average or above average general intelligence with certain learning or behavioural disabilities ranging from mild to severe, which are associated with deviations of function of the central nervous system. These deviations may manifest themselves by various combinations of impairment in perception, conceptualization, language, memory and control of attention, impulse or motor function'.
http://www.vernoncoleman.com/ritalin.htm
That condition is now called ADH, and this problem has been with us for very many years, under different labels.