The upcoming referendum has made discussion of relationship breakdowns, separation & divorce very topical.
This article from clinical psychologist Dr. Maureen Gaffney gives an insightful look at the topic in particular highlighting the mental & physical health costs to couples.
She highlights early intervention as key, as early as prior to marriage. Many clients I have worked with have described situations where relationship counselling & mediation were left until far too late and thus were ineffective or in some case made things even worse.
If repair & healing is what the couple want to work toward together, helping them gain understanding on relationship issues & patterns of negativity as well as learning new less destructive ways to communicate are some of the things that can be explored in therapy. Support can also be very useful for those going through the stress & turmoil of a difficult separation & divorce if a decision the end things is made.