In general longitudinal studies demonstrate that hyperactive symptoms typically attenuate by early adulthood, but inattention is much more likely to persist. Re

In general longitudinal studies demonstrate that hyperactive symptoms typically attenuate by early adulthood, but inattention is much more likely to persist. Reports vary somewhat, but around 1/2 of childhood cases remain diagnosable as adults, and a greater proportion, ~2/3 have persistent characteristic manifestations that adversely affect functioning. Getting treatment as an adult has become much easier in the last 10 to 20 years. Those of us in the "front lines" have pushed the cause and now it's seldom a problem, except to the extent health care coverage is a problem in general, but that's another issue. As a generic guess, if your brother still needed treatment when he was 18 or 19 years old, there's a chance he would have persistent functional difficulties, and if so, treatment could be useful. As always adequate assessment is necessary to know what's needed.