Reneg on Employment Contract

Any implications / complications associated (other than reputational) with backing out of a standard signed investment banking employment contract?

I have signed with one bank, but given the current macro conditions & uncertainty (and that bank / role's exposure to it) I think I'd rather go a different direction (different bank / role).

Assuming there aren't any serious repercussions with doing this, what do I tell them - something along the lines of given the deteriorating macro situation I don't feel comfortable joining you at this time etc.?