You don’t need to come on the first date and say “Hi my name is Meir. I smoke once a week, used to take ritalin, and got over childhood cancer when I was 3”.
However, lying and concealing are different things at different periods in dating. If someone asks you “Do you smoke” or “Do you go to therapy” “Do you take meds”, you need to say the truth IF you think the dating is going anywhere. You can’t evade the question or conceal it, and should be prepared if you do have an issue like that.
Concealing is ONLY ok if you’re not yet sure where this is going and don’t trust the other person. It’s not great but it’s understandable. Once you know where things are going, not telling them something you know they would want to know is dishonesty, plain and simple. It also shows that you’re not at peace with yourself and haven’t accepted the fact that you, like everyone else, has faults.
I think it’s really dangerous to play with dishonesty in the beginning of a relationship as well. But this is just an anonymous female’s opinion, not a Rov’s so of course you have to ask.