DinahMoHum is completely correct, but it hinges on one thing, whether you are baptized are not (as a JW).
If you are baptized (I was at 13), and subsequently want to leave the faith, you will be 'disfellowshipped' or you can effectively do this to yourself by 'disassociating'.
A disfellowshipped or disassociated person is not to be associated with by any members who are still JW (aside from absolute essentials, such as if you work in the same place, or you are still a minor living at home, etc.)
This extends to JWs being advised not to even say 'hello' to the person (based on a scripture that says not to greet such ones). If they ignore this advice, they risk being 'disciplined' themselves.
My mother became disfellowshipped, and was subsequently shunned completely by her entire family (including parents and adult children), until after two years of isolation she could not take the pain and returned.
The same thing has happened to two other more remote family members of mine, various members of the congregation at different times, and I am now in the difficult position of facing the prospect of this happening to me should I openly decide to leave (the only reason I haven't is because I do not want to lose my entire family).
It makes me very angry when Jehovah's Witnesses try to cover up or deny these consequences, as they absolutely do exist.
The only people who can leave without severe social consequences are those who have never been baptized.