This depends on several things. Convenience, how much you depend on other people for support etc. Honesty is usually the best policy - but timing is also important. Are you medicated or in therapy at all? Because it usually helps in explaining things. If they know that whatever condition you have is under control, it's a lot more reassuring for them. Not that being unsupported professionally means things are out of control; but that might be their main concern initially. If you're not receiving professional input i would perhaps be more casual with the details when necessary, especially earlier on in the relationship...if they're supportive and encourage you to share more, do so. But you need to be mindful of not putting too much expectation on them all the same. New relationships and a lack of understanding about MH can combine horribly but if dealt with carefully, there's every hope that things should turn out ok. Best of luck to you.