Yes, [FCM** you’d be a good friend if you tried to help this person. I certainly ought to have gone to see a medic long before I did.
I’d say, however, that it might just take a while for your friend to act on your advice, just letting the idea filter through slowly.
FCM being down in the dumps whilst not depressed always has an external stimulus causing it. Whether that is bad weather, job stress, a hurtfull comment, general anxiety about the upcoming war …
Being clinicaly depressed doesn’t need this external cause, it is internal chemical imballance in the brain.
The difference for the observer can be allmost impossible to see. I know that no one thought of me as depressed during my first 10 years of clinical depression, that was because the image I projected was often the opposite of what I felt.
So what can you do for your friend?
Well, be as close and trusting a friend as you can be. Communicate with them on the deepest levels about how you feel, and hope they open up to you. If they seem to be depressed by real things (the threat of war is effecting almost everyone these days) then that is fine and you can comfort each other. If the seem to be depressed by unreasonable things (they beleive they are useless, beleive no one really likes them, beleive they cause unhappiness in other peopl) then they may well be clinically depressed, and suggesting a trip to the doctor may be in order.
Hope this is helpful, Cheers Bippy
P.S. to give you an idea of depression’s affect on me.
I intellectually know that what I just wrote above, could be helpful, and is probably worthwhile.
I deep down know, that what I said is worthless, and will if anything cause you to upset your friend, and probably make you hate me for being insensitive and stupid.
Luckily for me I am intellectually strong, and also know deep down that my deep down feelings are warped and bad for me.
See it’s a complex situation 
Just seconding all the comments above about depression and its effects. It is not easily understood by those who haven’t “been there.”
One unhelpful thing that well-meaning (or maybe not so well-meaning) folks sometimes do is to tell the depressed person to just “snap out of it.” There is nothing the sufferer would rather do; unfortunately they often just can’t. It’s as effective as telling a diabetic to just stop being so lazy and start producing insulin like the rest of us. Adding to the misery is the stigma attached to mental ailments.
Having seen this gallop through my family, affecting my mother, sister, self, and one daughter, I am convinced that there is often a basic chemical imbalance in the body that must be addressed before any therapy is helpful. I was finally helped by a family practice M.D. who listened.
There is a big difference between looking at a beautiful day and being able to FEEL that it’s a beautiful day and enjoy it, and KNOWING that it’s a beautiful day that you should be enjoying but cannot. Thank you Paxil. It worked for me.
Please see if you can get your friend to find a doctor to provide a complete checkup to rule out any other physical illnesses, and to determine the best course of action.
These are my personal answers, obviously this isn’t everyones story.
Those are the two levels of depression I’ve faced. Ferret Herder’s version is what I’m still dealing with on a day to day basis. Well, I don’t have a husband, but… It’s hard, and I’m still at home with my family, which makes it harder, because as much as my mom tries to understand, she just can’t get it. People with depression know what I’m talking about… people who just don’t get it. It doesn’t completely go away on meds, they just help. They help a lot, but they help.
MissBungle’s definition is what promted me to get help after probably two and a half years. I thought I just had the High School Blah’s or I was just making it up for attention or something. But when I went numb, and started contemplation suicide, I knew it wasn’t just nothing.
It helps some people, but not everyone, and not completely. I know that having people there to listen helped me a lot, but there were a lot of things I felt I couldn’t share. Things that I couldn’t voice because they were irrational, and I didn’t even understand them.
And in other news, don’t think that eating too much and sleeping to much disqualifies you from being depressed. That was one of my mistakes. I would (and still do) binge eat, and sleep a lot, often falling asleep in class (still).
Medications take a while to figure out. I tried Paxil and Zoloft and got a nasty side effect called ackathasia (sp?). Moving moving moving. My shrink put me on Wellbutrin, and I’m doing pretty well.
And lastly, ignore people who say it’s all in your head. I’ve had people I know, trust, and love tell me all I need to do is pray, and that made me want to cry every time. People say the dumbest things about depression, especially if you’re open like me about it. I don’t see any reason to not discuss it with people, if the subject comes up, and it’s caused me to grow a thick (but not thick enough) skin about the subject.
Sorry about my long-windedness.