I just read (skimmed, actually) an interesting article called "Depression's Upside" at nytimes.com. Chances are, if you end up reading the entire thing, too, then you must be melancholic yourself.
Depression is one of those age-old phenomena that has been taken over by commercial interests who would like as many people as possible to think they have a problem that requires treatment. I prefer to divide what we today call "depression" into two categories -- pathological "depression" and normal "melancholy." Melancholy is the historical and more accurate term for what so many of us experience on a regular basis.
The article talks at length about research that shows that melancholy is associated with greater focus, creative output, and analytical thinking. It states,
In a survey led by the neuroscientist Nancy Andreasen, 30 writers from the Iowa Writers’ Workshop were interviewed about their mental history. Eighty percent of the writers met the formal diagnostic criteria for some form of depression. A similar theme emerged from biographical studies of British writers and artists by Kay Redfield Jamison, a professor of psychiatry at Johns Hopkins, who found that successful individuals were eight times as likely as people in the general population to suffer from major depressive illness.Wonderful. Surely this should be included as one of the "7 habits of highly effective people." Actually, it may already be implied. Who else would be predisposed to ruminate over their long-term goals, form "personal mission statements," and to spend time analyzing their behavior, attitudes, and assumptions? I'm sure Stephen Covey is himself depressed -- just look at his writing output. Something is clearly bugging him! In fact, all the people I know who've really gotten into Stephen Covey have been melancholic. Hmmm....
I laugh at this topic because I am myself a writer, am prone to introspection and extreme focus over long periods of time, and am highly analytical and generally perceived as a creative person. Melancholy is a normal part of my life, a valuable resource to be utilized but not overexploited. I owe many great ideas and wonderful decisions to my propensity to think long and carefully about things, introspect, and distance myself from social stimuli. I wouldn't trade my melancholy for a million dollars (indeed, to earn a million dollars in the first place one would have to be melancholic).
While I scoff at the thought of ever thinking of myself now as "depressed," there have been a few times in the past when I would have certainly qualified for the term. In each case there were objective causes -- always interpersonal -- to my protracted malaise.
Thanks to socionics, I became aware of the kinds of interpersonal factors that might have been causing my multi-month blues. I came to believe that the types of the people around me were having a great effect on my general emotional state, and that results could be obtained by changing the types in my environment by choosing more carefully whom I lived with, worked with, and was emotionally close with. This strategy worked! It took a couple years to make my "type environment" the way I wanted and to learn to stop nagging people with the "wrong" types to try to get them to start understanding and validating me. But since then, I have never had anything that I would call full-fledged depression.
And yet, the melancholy continued to come and go even as my life circumstances improved. I believe it has a physiological component that is built into my temperament, whereas my "depression" was the result of external factors that could be influenced or removed.
I observe that melancholics can be of any socionic type, and that many IEEs are not melancholic like I am. Melancholy seems to be something that is mostly or fully independent of type.
My experience is that melancholic IEEs tend to be introspective, slower-paced, and share more original thoughts. Those who lack the boon of melancholy seem to easily lose their train of thought, jump from topic to topic, and engage in more superficial conversation and gathering of random but "potentially interesting" data. They are more sociable and spend less time alone, thinking or working.
In general, melancholic individuals of any type seem to be a bit distanced from society, which is virtually a prerequisite to doing most kinds of creative work. One of the challenges in life for these individuals may be connecting with other people. At the same time, when they do connect, it may seem to be a deeper kind of connection than non-melancholics enjoy.
Most melancholics seem to need things to be "a certain way" so that they can work productively. Their special demands may make it harder to find a spot for themselves in the workplace, where conditions are adapted for the average person's needs (at least theoretically). On the other hand, given ideal conditions, the melancholics can be particularly productive and creative.
In terms of interaction, too many melancholics or non-melancholics together may be a bad thing. Melancholics may tire of the excessive seriousness, while non-melancholics may tire of the lack of substance. Both groups have something important to offer, and they tend to intermix to a degree.