What about these symptoms?  All of this is a part of depression much as a fever, diarrhea or inflammation may be part of some other illness.  you need not have all the symptoms listed here (or you may have different ones), but at least some of them are common to all depressions.

When did your Depression Begin? 

It may have begun long ago.  Physicians today treat many patients in their fifties, sixties or seventies who seem to have been depressed more or less continuously for their entire lives, ever since they were children.  On the other hand, some people acquire depression for the first time at some particular period in their lives.  It may begin gradually or suddenly.  It may go away and return or once it has occurred, it may continue without any relief.  Some people swing back and forth between periods of depression, periods of normal feelings and periods when they feel so elated that they know that this "high" in their mood cannot last.

How Long is Depression Likely to Last?

This depends on whether the depression is treated or not.  Without treatment, the depression may go away by itself after a time or may last forever.  With treatment, it is almost certain that the depression can be relieved within a reasonable period.  Through experience, physicians have learned to predict quite accurately what is likely to happen.  They usually can determine the nature of the depression, decide whether or how it should be treated, and forecast what will happen as a result of treatment after they have seen the patient a few times.

What sorts of Treatment are There for Depression?

Most depressions can now be treated adequately with a variety of medications.  A decade ago this was not true but in the intervening years chemists, pharmacologists and physicians have developed a large number of compounds that successfully control the symptoms of depression.  In rare cases electroshock treatment may be useful and for other patients psychoanalysis, but medications are usually quite sufficient.

Is Intensive Psychotherapy Necessary?

Many patients ask this question.  The answer is that in most cases the medications alone are sufficient to relieve a depression and it is not necessary to enter formal psychotherapy which is the treatment of emotional problems through discussion and understanding.  In a few cases the physician may recommend deep psychotherapy for the relief of certain emotional disturbances that complicate the depression or that are causing other kinds of difficulties.  Even in these cases, however the physician ordinarily will suggest that the psychotherapy be delayed until medication has relieved the acute symptoms of depression, which usually make psychotherapy difficult and unproductive.  A patient who is already receiving psychotherapy, of course, may be urged to continue.