Should I tell my future daughter in law?

Our mental health can vary and you say in the past your son had mental health issues. Lots of people do.

Presumably, he has conducted a courtship and found someone he loves and wants to marry without his 'past' problems causing his girl to question the state of his mental health.

Is their any certainty that his MH is likely to falter and cause him problems in the future? Perhaps he feels better, stronger, more confident and sure these days so for him, it IS in the past.

Without knowing his history it's hard to say if he is concealing problems, or has moved on from the MH episodes he had before, and is going forward from a much stronger place.

It is his duty to tell his fiancee if there are likely to be problems ahead though. I understand your worries however.

Presumably (from what you’ve written in your post) you have discussed this with your son and he has asked you not to say anything to his fiancée.
It would be a betrayal of trust if you did.
It’s an interesting question though.
If your son had a history of cancer, or a genetic condition like haemophilia, would he disclose that to his fiancée? And should he?

This something he needs to discuss with her. Should he ask your advice feel free to advise him as you think fit. However no, I would not say anything to your future DiL. Perhaps she knows more than you think anyway?

What a ghastly position to be in. I don't think you can say anything, unless she asks you direct, in which case you cannot lie.

babcha

That's your son's private information. I understand your concern. But it's his life. That's his information to share. If they're old enough to get married, they're both adults. It's up to them to disclose their personal health information to each other.