While all the signs/symptoms that 4tees has pointed out are common signs of depression, they tend to be more often associated with women who are suffering from depression than with men.
While women, when depressed, tend to feel hopeless, worthless, and to lose interest in their work, men on the other hand tend to feel irritated/frustrated, work excessively, and to display aggressive behavior. Some in the medical community suggest that the different symptoms diplayed by men who suffer from depression is one of the reason why it is often misdiagnosed (or not disagnosed), because their symptoms (such as agressivity) tend to be seen as men's normal way of dealing with stress. Of course, this doesn't mean that all men suffering from depression will disply those same symptoms: but aggressive behavior is one of the more common signs of depression in men.
As usual, Lady Genevieve hits the nail right on the head. Men suffer depression differently than women, and symptoms vary person to person. Myself, I have suffered from it (or possibly dysthimia (a chronic lower intensity depression) since the early 90's. I've only started taking action on having it addressed since around November.
Look at some of my posts from November and December of last year. I was frustrated, irritable, angery, miserable, lonely, worked myself to the bone, frequently skipped meals, sleep was at a minimum, and regularly engaged in pointlesly reckless behavior. A lot of my coworkers didn't believe I suffered from depression, as I was usually energetic, bright and joking. My family still barely recognize it, and generally attempt to change the subject should I wish to talk about it.
One of the big things to look at is your sense of self worth, or self esteem. Your phyical symptoms could be from other possible causes as well. But a sever drop in self esteem, or lack there of, is a pretty good indicator.
I have been doing group therapy since around Febuary, and that has been useful. Cognative Behavioral Therapy (CBT) is quite interesting, rather enlightening, and can be quite difficult. But I have come to realize just how messed up/distorted my thinking really is. I now realize how out of whack my thining is, in regards to myself, but adjusting for it is difficult.
Also around Febuary, I was started on Cymbalta. It felt like a dark fog had been lifted off of me. Sure, I was still somber and extremely prone to beating up on myself, but the filthy malaise that hung in my mind was gone. There were two long lasting side effects though....First being my sex drive decrease. Second, I started having difficulty...ummm....'finishing', this in turn drove my sex drive even lower.
Two weeks ago, I mentioned this to my psychiatrist, and he prescribed Welbutrin. The first week, I didn't really notic much of a change. Now just to give you an idea what my sex drive was like on the cymbalta. I'd see an attractive woman, and I would apperciate her...Like a glass of wine, or a well designed car...Intellectually. Now I see her, and part of my brain goes "
WOMAN, and I feel a physical responce too. There's been a couple of days I've been so horny I could have plow a feild. (I'll tell ya, if the delaying side effect of cymbalta coincides with a bout of welbutrin horniness, and given my recent physical conditioning, I'd feel sorry the lady that crosses me)
I may be medicated, and feeling better, but as my doctor said, we still have to deal with my self hate.