I can really only offer a few thoughts, ed ,from anecdotal evidence and would not claim that they would be validated statistically.
some people leave a church after an upset, or other personal reason but still retain their faith otherwise. it would be my expectation that their faith would continue to inform their morality.
those that leave their faith altogether sometimes do so in tamden with disobedience to biblical morality.
for any that lose their faith for intellectual reasons [I understand that Piltdown man fraud did some damage, for eg] I suspect morality may slide over time, but again that is not an assertion.
I don't think I could speak for other faiths, except to observe that many of them are tied to their culture and so perhaps MAY not be so deeply committed. of course the same can apply to Christian affiliation , and mafia may be a case in point.