Hi, Someone very kindly sent me a link which was for the Official ESTA Application Website, U.S. Customs and Border Protection (dhs.gov) and on here it states what you have pointed out about the behaviour which in my sons instance would mean the answer to the question is no thankfully! Thanks for taking the time to reply. This was the answer the site has is as follows, am pasting it here in case it's helpful for others. Will be submitting the application this afternoon so fingers crossed it goes through!. Also have double checked the Canada travel document situation but as he is cruising in and not flying in he doesn't need a visa.
Physical or Mental Disorders
With regard to physical or mental disorders, answer "Yes" to this question if:
You currently have a physical or mental disorder and a history of behavior associated with the disorder that may pose or has posed a threat to your property, safety or welfare or that of others; or
You had a physical or mental disorder and a history of behavior associated with the disorder that has posed a threat to your property, safety or welfare or that of others and the behavior is likely to recur or lead to other harmful behavior.
Answer "No" if:
You currently have no physical or mental disorders; or
You have or had a physical or mental disorder without associated behavior that may pose or has posed a threat to your property, safety or welfare of that of others; or
You currently have a physical or mental disorder with associated behavior, but that behavior has not posed, does not currently pose nor will pose a threat to your property, safety or welfare or that of others; or
You had a physical or mental disorder with associated behavior that posed a threat to your property, safety or welfare or that of others, but that behavior is unlikely to recur