According to an ongoing study published in the journal "Family Relations," a strong relationship with a husband and a mother-in-law (or father-in-law) can decrease the couple's divorce risk by 20 percent, says CNN.com. The wife often appreciates her husband's close relationship with her parents, viewing it as a validation of the couple's closeness.The husband generally finds this relationship rewarding rather than threatening. Friction between a husband and his mother-in-law on the other hand can put the wife in a difficult situation, where she feels she has to choose between two loyalties.

Surprisingly, the same study showed that wives who have a good relationship with their mothers-in-law actually have a 20 percent higher risk of divorcing. This may be for several reasons. Even wives who get along with their mothers-in-law feel more threatened by them, and worry that they will interfere in the marriage relationship. In fact, the very fact that the mother-in-law feels close to both halves of the couple can make her feel more comfortable meddling or crossing boundaries in the relationship. Because the daughter-in-law may not be able to set clear boundaries with a loved mother-in-law, this can negatively impact the marriage relationship as well.

Mothers-in-law rarely believe that they are meddling in their children's business, but many daughters-in-law feel that without firm boundaries, their mother-in-law can actually destroy their marriage. Some mothers-in-law feel that their years of experience can help the fledgling family succeed, and they will therefore offer advice or help in situations where it is unwanted -- especially homemaking and parenting. Lois M. Collins in her article "Relationship With In-Laws Impacts How Long Marriage Lasts," explains that even when in-laws hold back from giving advice, a simple comment such as "So, when are you thinking of potty training him? He's already three!" can be taken in a negative vein.

In order to minimize the negative effects that a mother-in-law may have on your relationship, make sure to set firm physical and emotional boundaries. That might mean saying "no" to your mother-in-law if you don't think that saying "yes" will benefit you as a couple, recognizing that your mother-in-law probably isn't hiding an insult in most of the comments that you view as negative, and listing ways that you and your mother-in-law are different -- and will probably always be different. Having your husband on board and supporting you is also crucial to keeping the peace, explains Dr. Teri Apter in an article in Psychology Today.