Answer by expert Gail Saltz, M.D., a psychiatrist, columnist, bestselling author, and television commentator.It’s pretty important. Most marriages go through periods when sex is better or worse, more or less frequent, but when sex dwindles to once a month or less, many couples report being unhappy in their marriage.Sex is an expression of intimacy, love and trust with your partner. If one or both partners are distressed by a lack of sex, that feeling can erode away other positive feelings within the relationship.Sex is what makes your relationship different from being friends, roommates or co-parents. The only couples who say they are really fine with a sexless marriage are those who have no interest or desire for sex. Even then, the lack of intimacy can put an end to the relationship.Libidos diminish for a variety of reasons, from anger or boredom with your partner, to exhaustion, stress, medication side effects, a health condition or hormonal issues. Unfortunately, most people never address the loss of desire and hence the issue doesn’t get treated.If there is a loss of interest for one or both of you it’s very important for the future happiness of your relationship to get some help, whether in the form of medical treatment or couples therapy. A deteriorating sex life is easier to rectify if you attended to the problem as early as possible instead of going for a long time without sex.