460-375BCE - Greece - Hippocrates on people who couldn't focus but were good at reacting to events - attributed to an "overbalance of fire over water"

1693 - Scotland - John Locke - in "Some Thoughts Concerning Education" - discussed a class of students who "could not keep their mind from straying"

1798 - Scotland - Sir Alexander Crichton - "The Disease of Attention"

1800s - Various - Medical Textbooks of the time - referred variously to conditions “nervous child”, “hypermetamorphosis”, “mental instability”, “unstable nervous system” and “simple hyperexcitability”

1902 - England - Sir George Frederick - describing the same systems named the condition an “abnormal defect of moral control”

1937 - USA - Charles Bradley - first began experimenting with prescribing benzedrine (an amphetamine) to Children initially for headache and noted that it greatly improved focus in those who previously had not demonstrated that ability, but could not explain why stimulant drugs could induce a calming effect.

1944 - Switzerland - Ritalin developed (Methylphenidate, Rita from his wife) as a safer replacement to benzedrine

1968 - USA - DSM-II lists these by now well recognised and medicated symptoms as "hyperkinetic reaction of childhood"

1980 - USA - DSM-III - changed the name to "Attention Defecit Disorder"

1987 - USA - DSM-III (3rd edition) - changed the name to "Attention Defecit Hyperactivity Disorder"

1994 - USA - DSM-IV - refined the disorder into it's currently diagnosed form with 3 different types of ADHD, namely: Inattentive Type, Hyperactive/Impulsive Type and combined type.

2013 - USA - DSM-5 - refined to acknowledge that the 3 different types are not in fact types, rather presentations that can change over the course of an individual's life.

or...

maybe it's a newly invented fake phenomenon

ps - not a response to the comment preceding :)