Masturbation is the deliberate stimulation of one's own genitals to achieve sexual arousal and pleasure. In one recent national study, 95 percent of men and 89 percent of women reported having masturbated. It is the first overt sexual act for the majority of men and women, although more women than men engage in sexual intercourse before they ever masturbate.

Masturbation Is a Common Sexual Behavior

Most men who masturbate tend to do so more often than women, and they are more likely to report always or usually experiencing orgasm when they masturbate (80 percent and 60 percent respectively). It is the second most common sexual behavior (coitus being first), even for those who have a regular sexual partner.

Still, men and women alike often express concerns about masturbating, says sex and relationship expert Dr. Drew Pinsky. "Men tend to worry about the frequency with which they do it," says Dr. Drew. "That, of course, is determined by the age of the male." A young man without a regular sexual partner, for example, might masturbate once or twice a day. He may even maintain that pace once he has a regular partner. "Obviously, most reduce that behavior, sometimes to essentially none, though it is normal for couples in relationships to masturbate as well," says Dr. Drew. As men age they tend to masturbate less.

Despite some negative associations with masturbating, "it is exceedingly rare for a male not to masturbate," says Dr. Drew. Even those that don't would likely have nocturnal emissions. Men who have never masturbated and have no nocturnal emissions should be checked by their doctor to make sure they don't have a problem producing testosterone or another endocrine disturbance.

And while men's masturbation behavior tends to be relatively similar, women are extremely diverse in how and when they masturbate. "Most women experience no urge to masturbate and no pleasure in masturbating until they are in their early 20s," says Dr. Drew. "This tends to correspond with their tendency toward orgasmic function, although there are some women who begin much earlier and have complete orgasmic function at a much earlier age."

Some women never masturbate. "In my experience these women tend to need intimacy in order to function sexually," says Dr. Drew. "That is to say, those parts of the brain that are associated with sexual arousal and orgasm are very deeply connected to emotional mechanisms and systems associated with intimacy." For these women, "trying to have a sexual experience alone becomes confusing and potentially even uncomfortable." Unfortunately, women often feel the need to live up to an unrealistic standard set by a highly sexualized society. "The standard that most commonly is depicted in our culture is the 17-year-old male, which is a profoundly different biological system and presumes a uniformity of biological function amongst women, which is absolutely untrue," says Dr. Drew.

Most children — often from the time they are infants onward — find the occasional stimulation of their genitals sensually pleasing, but do not come to understand this behavior as "sexual" until late childhood or adolescence.

During adolescence, the percentage of both sexes who report masturbating increases dramatically, especially for males. Most people continue to masturbate in adulthood, and many do so throughout their lives.