Though I'm not a psychiatrist, psychologist, therapist or trained mental health professional, over the course of my practice, I have noticed that the same reasons for a marriage falling apart present themselves over and over. 

Each one of these common marriage killers chips away at the foundation of a marriage:

1. Abuse. This is not just physical abuse, mind you. It includes psychological, emotional and financial abuse (yes, financial abuse is a thing). 

2. Narcissism. Narcissistic personality disorder is a disorder in which people have an inflated sense of their own importance and a deep need for admiration. Those with this disorder believe they are superior to others and have little regard for other people's feelings, though they are vulnerable to the slightest criticism. Though there are undoubtedly other mental health issues that tear at the fabric of a marriage, many can be resolved or are tolerable so long as there is appropriate treatment. To me, narcissism seems to be a different story, particularly because it is almost impossible to treat, let alone "cure."  Woe to the spouse of a narcissist who will not allow themselves to be a doormat for the rest of their lives. Initially compelling and beguiling, life with a narcissist can quickly become a nightmare when their parasitic lifestyle, self-involvement, and lack of empathy chip away at the self-worth of their spouse.

3. Empty Nest, Empty Marriage. Once the babies are off to college or close to it, and a couple's energies are no longer focused on raising the children, they may find that they have been living as roommates for years and are strangers to each other. Moreover, a spouse who stayed home to raise the kids and forewent their career or other interests may find themselves spending a lot of time with someone else they do not know – themselves. If the marriage has been allowed to stagnate or deteriorate during the years that the couple was raising children, one or both spouses may find that they are left with a marriage that is beyond repair.

4. In-Law Interference.  When a spouse has not cut the cord, especially if the in-laws live close by, the marriage sustains a lot of damage. In an recent British poll, 11 percent of those polled blamed interfering parents-in-law as the “main” cause of their divorce. One finding of a 26-year longitudinal study of married couples is that marriages in which the husband initially reported being close to his wife's parents, the risk of divorce over the next 16 years was 20% lower than for the group overall. Bizarrely, when the wife reported being close to her in-laws, that seemed to have the opposite effect: the risk of divorce with those couples was 20% higher.

5. Addiction. Addiction in all of its forms wreaks havoc on a marriage. Not just alcohol, prescription and non-prescription drugs, but also gambling, pornography and sex addiction and even spending addiction. The personality changes that accompany addiction, as well as all of the lying and risky behavior that comes along for the ride, can destroy marriages and families.

6. Adultery. This is the marriage killer that people usually think of first, though many, many marriages can survive a one occasion dalliance with therapy and a commitment by the couple to repair the damage. However, many marriages cannot survive infidelity, whether it be multiple betrayals or a one-time mistake.