You can be diagnosed with the condition called Attention Deficit Hyperactive Disorder or ADHD at 4 years old.
Most children aren’t checked for ADHD until they reach school age. However kids as young as 4 years old can be diagnosed, according to guidelines set by the American Academy of Pediatrics (AAP).
That said some adults that were not diagnosed with ADHD as a child can still get diagnosed with adult ADHD well into their adult life. You can do a test for ADHD here.
Some people had no idea that they had the condition, even though they suffer massive impacts like broken marriages, more car accidents, difficutly holding ajob and many more disadvantages.