ADHD Diagnosis Criteria

 Very new to all of this and grateful to have found this site. Married 13 years and miserable most of that time. My husband is 65 and displays most of the classic symptoms of ADHD. Can't remember anything, loses track of time, unreliable, misplaces things, absent from the marriage... the list goes on.
 

At my insistence he recently had a full neuropsych evaluation that found no problems with early dementia, intelligence or memory. They noted that he has adult ADHD tendencies but could not give the diagnosis because - wait for it - he *couldn't remember* having ADHD symptoms before age 12. His parents are both gone and his oldest sister can't remember either. Is it true that he can't get an ADHD diagnosis (and, therefore medication) if nobody can remember if he had early childhood symptoms? He hasn't seen a psychiatrist yet but is it even worth it if we don't have the early childhood piece? 
 

I am beyond frustrated at this point. Thanks for any insight.