Most people describe experiencing relatively high levels of sexual desire when they enter into new . As a therapist, I've heard countless couples reflect fondly on how they couldn't keep their hands off one another when they first started . However, most people also find a high level of sexual passion difficult to maintain as relationships progress.

But, how exactly does sexual desire change over the course of a relationship? What about after ? After having kids? And do men and women experience these changes similarly or, perhaps, are there some possible differences?

Relationship Duration and Sexual Desire

A few years ago Dr. Robin Milhausen and I conducted a study in which we examined whether the length of time men and women were in a relationship influenced their levels of sexual desire.1 Our study included 170 undergraduate students (91 women and 79 men) between 18 and 25 years old, in relationships ranging from one month to nine years. We found that while men reported high levels of desire regardless of how long they had been in their relationships, women reported lower levels of sexual desire the longer the length of their relationships.

However, there were two important limitations of our study. First, the sample was relatively young and may not have experienced the same stresses that some of us might consider part of "real" long-term relationships (such as being married and having kids). Secondly, the data was taken at one point in time so we don't know what (if any) changes might happen as these particular individuals progressed in their relationships.

The good news is that research is always evolving and researchers of a new study have some answers to fill in these gaps.

The New Research

In a new study just published in the Archives of Sexual Behavior, researchers used data from two longitudinal studies to explore how male and female sexual desire might be impacted in the early stages of marriage.2 One study included 72 heterosexual couples (144 participants) and the second included 135 heterosexual couples (270 participants); all participants were recruited in the United States.

Participants were provided with several questionnaires shortly after getting married, and then every six to eight months after marriage for a total of seven points in time. At baseline, newlyweds reported moderate to high levels of desire on average, with men reporting higher levels of desire than women.

Other the course of the next few points in time, however, women's sexual desire declined more steeply while men's sexual desire did not show a decline on average. The advent of children accentuated this difference, such that new mothers reported a greater decrease in sexual interest while men's desire again remained constant on average. These findings held even after controlling for and -related to .

It's worth noting that this pattern was also the same whether the participants were reporting on their desire for their partner or their sexual desire in general.

Interestingly, despite decreases in women's sexual desire not having a significant impact on reported sexual frequency, decreases in women's (but not men's) sexual desire was found to have a negative impact on men and women's sexual satisfaction as well as their marital satisfaction.

Do These Findings Support Traditional Ideas About Women Having Weaker Sex Drives While Men "Always Want Sex?"

Not necessarily. It's tempting to conclude that these two studies reinforce the stereotype that women have weaker desires while men's desire is high and constant. In fact, evolutionary theory has been used to support the idea that once women enter into a committed partnership and have children, their focus shifts away from sex, while men are wired to "spread their seed" regardless of these factors.

However, there could be other explanations. First, research suggests that men may have a difficult time admitting that they feel a decrease in sexual desire as this goes against the grain of what men are "supposed" to experience based on limited, yet pervasive, social norms. In that sense, it may be that men do experience lower or decreased desire but simply aren't comfortable reporting it. Second, Dr. Wednesday Martin, an anthropologist and author of the book Untrue, posits that long-term relationships may be particularly hard on women's desire. She suggests that women (perhaps even more than men) require variation in their sexual experiences to maintain their sexual interest in the context of long-term partnerships.

Take Away

Whatever the reason for these differences in sexual desire, many mixed-sex couples do experience desire discrepancies. The findings from this new research suggest these differences may increase over the course of a relationship. It may be reassuring for some to consider that these sexual problems are more of a natural occurrence rather than signaling a serious relationship problem. However, sexual discrepancies can still cause significant sexual dissatisfaction and marital problems. Working with a therapist to navigate these differences could be a helpful place to start.