I agree that an affair is an addiction. However, the reason for the addiction is critical--is it because the person is addicted to affairs, or because their marriage is weak, or (in the case of an MLC) because they've become zombies in the wake of a critical event like the death of a loved one, and a new partner is only one of the addictions they've sampled in order to feel alive again? In the last case, addressing the affair will not lead to "beginning to address the overall marital dysfunction" UNTIL the depressed spouse is ready to recognize that s/he is running away from him/herself, and is able to begin dealing with his/her pain.
If that's the timeline (multiple addictive behaviors, infidelity is only one of them, and some "life crisis" came first), then I agree. It's also true sometimes, however, that thru "re-writing of marital history," a cheating spouse will pre-date their affair and claim that "Oh, I've been unhappy for a long time now," or "I emotionally divorced you a long time ago, so it's not really cheating," etc.
