We might see increasing forgetfulness in older age as a red flag of mild cognitive decline or dementia. But it turns out that some of the cognitive symptoms may be manifestations of a lifelong condition: attention deficit hyperactivity disorder (ADHD). As psychiatrist at McLean Hospital Stephanie Collier writes for Harvard Health, while we often think of ADHD as a childhood disorder, it can also affect older adults. In fact, about three out of every 100 older adults has ADHD.