Im sorry by documents I mean like this

Documents Needed to Enter US or Canada | ezbordercrossing

if you have all the required documents chances are the questions that they ask wont be so uncomfortable. they see that all your documents are in order and you are not acting suspiciously the odds are in your favor.

as for the criminal background check a suggestion contact the treatment providers that hospitalized you and such wrongfully and ask them for a copy of the release papers, go to the police and get a copy of the form that says you did not commit the crime due to mental illness. I know a few people who did this and no longer have a problem crossing borders because they have the correct documents.

you can also petition the court to have your record expunged. this is where you prove though you may have had those problems in the past but you have changed. the court will require statements from your friends / employers/ and anyone else that knew you when and know you now and can make a statement to the court to how you have changed. you may need to talk with treatment providers too. if the court is satisfied that this problem no longer needs to be a part of your records they send out orders to everyone who has kept a file on you, notifying them that your past is expunged and can no longer be used against you for anything including background checks, that the files have to be destroyed. once the court orders all the files destroyed about that situation it will no longer be accessible.

Reading about the Canadians who were refused entry due to mental health was very disturbing. I wonder if there is a way we can know what records border control has on us? It's possible they just have a note that you were arrested and you got pulled into the office because your answer didn't match their records. I suspect there is some kind of flag next to my name because I am stopped and searched frequently since traveling with someone who gave the wrong address - he had one thing on his license but had recently moved.