Unfortunately, nothing can change until he wants it to. As long as his mind is closed to the idea that there’s more than depression, nothing you say or do will likely make any difference.
The good news is that he thinks he has ADHD. Would he be open to reading about ADHD? Something that could help him recognize some things in himself possibly… like “Driven to Distraction,” “You Mean I’m Not Lazy, Crazy or Stupid?,” or “The ADHD Effect on Marriage.” Don’t tell him he has to read something. Just leave it lying around the house. All of those books would be a good read for you as well.
ADDitude Community Moderator, Parenting ADHD Trainer & Author, Mom to teen w/ ADHD, LDs, and autism