Sexual Relationships 
Sexual Health 
As a psychology student and daughter of a very experienced psychiatrist, I have noticed a rise in single males getting depression. The reason is the same in many cases: Sexual frustration.
These men simply aren't satisfied with their sex life and it has a great impact on their mental state. Actually, the frustration is also mental, not physical. It's not like these men never had sex, most did. Just not enough, not with enough partners and not the type of sex they want to have. And to be honest, I think it's the casual sex culture of today that makes them depressed.
When you put society's sexual behavior in numbers you get some striking results. All single women ages 18-35 seem to have sex about 3 times a month on average. Since there is a large pool of 35% of single women that doesn't have sex outside a relationship, that means the ones that do, do it quite often (I can confirm that myself being in college lol). Especially for being single. Also the number of sex partners a woman has by age 30 is now a lot higher than a decade ago. About half the women have double digits.
I don't have an average number of how often all male singles have casual sex on average, but we do know that only 20% of single men have had one or more casual encounters. Most of them only had sex outside a relationship a couple times. Only a very small amount of these men admitted to have casual sex extremely often (more than once a week).
So overall, and I concluded that from patients themselves as well, single women (18-35) have a very active sex life. Single men on the other hand, except for those lucky few, have an almost none existent sex life. That by itself shouldn't be the biggest problem. But today there is an attitude that everyone should be having casual sex, that it's very common and normal. It is, for most women, not for most men. Media constantly pushes it in our faces and through social media, some brag about their success. And when a man feels that he is sexually not as successful as the norm, he feels like a loser, a failure, and gets depressed.
Another factor that plays a role, is ownership. As ridiculous as it may sound, men connect sex with ownership. When they have sex with a woman they have (some more than others) the feeling that they own that women, like they conquered her. If they can do it without a commitment, they feel like they definitely own the woman, and they feel superior to the men that have or will commit to that woman. In fact casual sex seems to give a much larger ego boost to a man then doing it with a commitment.
So while most men don't get many partners in bed, they know those few superior guys are out there owning pretty much all the women, putting their mark on them and ruining them for when they one day might get a chance with them, probably through commitment. Guys have a strong sense for sexual competition (check sperm competition). Some anti-feminist groups like MGTOW (they are completely crazy though) have theories based off this. With the current casual hookup culture, this situation has become pretty hopeless for the large group of single men.
So the combination of the ownership issue and the feeling like they don't make the norm because of media spreading the commonness of casual sex, makes single men seriously doubt their sexuality and this seems to get them very depressed. If you are a single man and feel like this, I hope my take on this will make you feel a little better, because remember, you are not alone.
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