There is a major problem with the diagnosis of "depression," and this is that it doesn't exist. There is such a thing as "melancholia," a very serious from of depression entailing risk of suicide and complete lack of pleasure in life. But, hey! for years this illness was called by its proper name, melancholia, and there is no reason why we can't continue to do so. Melancholia is, in fact, in the Diagnostic and Statistical Manual of the American Psychiatric Association, the famous "DSM," but as a subtype of major depression.
Still, if you don't have melancholia, what do you have? Depression? Remember that depression means a mood disoder. High mood would be euphoria, or some form of mania. Low mood would be sadness. But the problem is that many people who get the diagnosis of major depression aren't necessarily sad. They don't cry all the time. They drag themselves from bed and go to work and plow through family life, but they aren't sad. They may well have one of the "D-words" – dysphoria, disenchantment, demoralization – but they aren't necessarily depressed.
Instead, what do they have in addition? They're anxious. They're exhausted and often report crushing fatigue. They have all kinds of somatic pains that come and go. And they tend to obsess about the whole package.
What they have is a whole-body disorder, not a disorder of mood. And that is the problem with the term depression: it shines the spotlight on mood, a spotlkight that belongs elsewhere.
Medicine once had a perfectly good term for this kind of whole-body disorder that involved a down-ish mood, plux anxiety, fatigue, somatic symptoms, and an obsessive interest in one's condition. It was called nerves, or nervous illness. In the extreme form of nerves, comparable to melancholia (which really is a disorder of mood), had a nervous breakdown: You couldn't function. You'd be a candidate for admission to a private nervous clinic if you had the money. But short of a breakdown, millions of people were once considered "nervous." Today they receive the diagnosis of depression and are treated with "antidepressants."
I'm not holding out for the reinstation of nerves as a diagnosis. As a historian, I like its solid ring over the decades and centuries. Yet, other may find nerves antique and prefer another term – a neologism like "dysthymia" (Peter Tyrer's idea). But it's important to get the spotlight off the term "depression," indeed to abolish it because it represents a heterogeneous patient pool. Some of the patients have melancholia, a disease of its own with distinctive biochemical markers; other patients in the pool have what is often called "depression" today, but their symptoms and clinical course will be quite different from those of the melancholics, and they require different treatments as well.
The term depression means that everybody gets the same treatment: Prozac-style "antidepressants," ineffective for melancholia, mildly effective for anxiety and obsessiveness (which people diagnosed with depression may well have). But indication-specific treatments are called for here: electroconvulsive therapy (shock treatment, ECT) and tricyclic antidepressants (such as imipramine) for melancholia; and for nerves, such effective but now abandoned drug classes as the benzodiazepines (Valium). Treatment specificiety means progress. Ditching "depression" is a way to begin.