We're humans, deep inside we contain strong emotions (some more than others) from which come love. When ever we fall in true love, we see extreme potential in a female that could be part of our lives, and trust me, we barely think about sex at first when it comes to love. We invest time in them, care, and thought. Our mind wonders off and place pictures of her in our mind. We feel an ecstasy every time she smiles to us, and an unexpected but wanted text from her can put us on a high for days.
Some wold call us obsessing maniacs, but we do not become insane --unless all of that is taken away. Unless we're lied with emotions, and we feel extremely betrayed. If we love someone, but she's unaware of it, nearly every single action she does will influence our day. If we're not loved back, we feel dissapointed with ourselves, and desire not to speak with anyone for weeks. We feel broken inside when ever stuff like these occur.
At least, most of us are like that, myself included. Some others are just emotionless monsters.
I guess what makes depression worse for guys is that we usually have nobody to talk to and if the do, we get ridiculed and told to "man up". This is one of the reasons why so many more men commit suicide than women.
Constantly being bombarded with "man up" is one of the reason why young men become depressed. Not allowed to be a human being with feelings and ridiculed if emotions are expressed in any way except in anger and violence.
Boys and men have to carry so much emotions all by themselves, we often break.
Practically the same thing that makes you depressed we are not allowed to show it due to societies standards. Naturally we are more aloof however i have seen countless times where the girl was doing completely fine and the guy was obliterated by the fact he had just lost his love. This stemms from the fact that women tend to be a mans emotional support... so when you remove that, he has no one to go to.