Telling my ADHD husband he had ADHD: How and when?

I know that my husband has ADHD, but he does not. I am trying to figure out how to talk to him about this diagnosis. I can say he has it with confidence because I am a psychotherapist. This only makes it harder to talk to him about social and emotional issues because he does not want me using my "therapy" on him. How do I get this information into his brain? It is at the core of our marriage difficulties and after 35+ years of marriage, I am not sure we will make it one more.