Sexuality.

Ian Kerner, a sexuality counselor and New York Times best-selling author, blogs about sex on Thursdays on The Chart. Read more from him at his website,GoodInBed. When men don’t want sex “Not tonight, honey. I have a headache.” How many times has a guy heard that before? Husbands around the world are all too familiar with being sexually rejected. But now, more than ever, those words, (or some variation), are being expressed by men, to their female partners. While the conventional wisdom has been that it’s usually the woman in the relationship who inevitably loses interest in sex, the opposite is often true. Low male desire is at all-time high, and is likely to occur for any number of reasons: Biological. There are many possible physical causes of low male sexual desire, from heart disease, to antidepressants, to alcohol or drug use, to low levels of testosterone. If he’s ruled out other factors, it’s a good idea for him to pay a visit to his doctor. Emotional. A guy’s sex drive is often closely tied to his self-esteem - when one suffers, so does the other. The economic downturn has sent lots of men into a funk: Job changes or loss, financial worries, and depression can all add up to a low libido. He may feel like less of a man, no matter how much his partner tells him that money doesn’t matter. Relationship. Feelings like anger, resentment, and general dissatisfaction with his relationship can play havoc on a man’s sex life with his partner - but these issues don’t necessarily sink his libido. Sure, he may claim he’s not in the mood. But he may simply be putting his sexual energy elsewhere, whether into masturbation, porn, strip clubs, or an affair. What happens outside of the bedroom affects what happens inside the bedroom, and when men are bored in their relationship they tend to get bored in the bedroom. Porn. The Internet has made porn much more accessible - and the frequent masturbation it triggers may be making men too worn out for sex with a real partner.As I’ve discussed before in this blog, men are masturbating 50 to 500 percent more than they would normally without Internet porn. So if a guy normally masturbated once a day, he might now be doing it two or three times a day. If he masturbated three times a week, he might now be getting graphic with his graphics 15 times a week. If you’re 17 and single, this might not be a problem. But if you’re 40 and toting a gut, it’s an issue - a real issue. Some guys may still feel mentally like they’re 17 years old, but they can’t have sex that way. Their bodies have changed and so have their refractory periods, the natural interval between erections. Guys with low desire may simply lack the mojo for real sex because they’re depleted from masturbation. Your relationship itself could also be contributing to his low desire. While there are similarities between how men and women get sexually aroused, there are also some key differences. New research suggests that female sexual response depends on the quality of emotional intimacy and overall relationship satisfaction. That means that when a woman feels comfortable and secure in her relationship, she’s likely to feel more sexual desire - to the point where curling up on the couch in sweats and a T-shirt is more of a turn-on than donning some sexy lingerie. But for men, this sense of complacency and comfort could work against sexual desire, especially if there’s less emphasis on novelty, newness, excitement, and visual stimulation, all of which play heavily into the stimulation of dopamine, a neurotransmitter that, like amphetamines, plays a big role in sexual arousal. Sex ruts and mismatched libidos are common in any long-term relationship, but guys are generally more used to striking out and not taking it personally. We play the numbers and we know we’ll get another chance at bat, so it’s more a matter of continually stepping up to the plate. But when a man is disinterested in sex, a woman is much more likely to take it as an insult or a reflection on her attractiveness, rather than looking at all the factors described above. Also, statistically, women are more likely to self-silence and bottle up their emotions than are men. So whereas a guy who wants more sex might lash out and say, “How come we never have sex anymore?” a woman is more likely to let her anger simmer and stew, which leads to resentment and might cause a woman to build an emotional wall between her and her partner, which will protect her from feelings of rejection. But the truth is that sexual desire is not a light switch that just gets turned on and off. The media tells men over and over that women need more foreplay. But women also need to get with the same program and understand that male desire is like a dimmer switch: It unfolds across a spectrum and requires effort. Men are not just walking erections, ready to go whenever the wind blows. Regardless of your gender, when a couple is dealing with mismatched libidos, the worst thing the partner with more desire can do is to give up on sex. Like Sherlock Holmes, the partner with more desire has to engage in some forensic analysis to uncover the clues and causes, and then take action to bring sex back into the relationship. From foreplay to fantasy, to enhancing communication and the overall quality of the relationship, there’s a lot you can do to foster a satisfying sex life. So start talking with each other, share a fantasy or two, and take a few aspirin for that “headache.” Your relationship wi February 24th, 2011 09:49 AM ET ======================================== ll thank you.And if you need a little extra help getting sexually creative,  check out the Good in Bed Guide to 52 Weeks of Amazing Sex.