[tunesmith]

This is interesting to me because... is there even a scientific definition of depression yet? Such that, if you have a defined list of symptoms, you are definitely depressed, and if you don't, you are definitely not depressed?

If not, we're at best talking about a magnitudinal thing or a probability thing. Like a Bayesian thing where each symptom's presence updates the probability of the person being depressed, which is turn based off of a database of previous cases of diagnosed depression and what symptoms they had.

But even that may be circular, ultimately. It could just as well be that depression is a vague category of similar symptoms that each come from a wide variety of scientific causes.

This is not to be mistaken for saying it doesn't exist or that it's all in someone's head - it's more just to say that if someone has depression, they have something that may deserve treatment and sensitivity, but that it's something that we still do not know exactly how to describe or diagnose, and so therefore we will just call it "depression" in the meantime. But what if we've sort of collectively forgotten the "in the meantime" part?

[ggchappell]

> This is interesting to me because... is there even a scientific definition of depression yet? Such that, if you have a defined list of symptoms, you are definitely depressed, and if you don't, you are definitely not depressed?

It depends a bit on what you mean. In the U.S. at least, diagnosis of depression is generally based on the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM).[1] That lists a number of disorders that would be categorized under "depression", including "Major Depressive Disorder", "Dysthymia", and the catchily named "Depressive Disorder Not Otherwise Specified".

In the DSM, these disorders are all treated as syndromes, meaning they are defined entirely by symptoms. They may have organic causes (troubles with neurotransmitters, etc.), but the definition of each disorder does not address that issue. This is in contrast to something like influenza, which refers to a particular organic cause (infection by a certain kind of virus).

As for the actual definitions, they vary in how specific they are. Major Depressive Disorder is quite specific, requiring certain kinds of episodes to occur with specified frequencies and lengths. On the other end of the scale is DD-NOS, which is essentially defined as a depression-ish thing that doesn't fit into any of the other categories. (Okay, it's a little more precise than that, but, honestly, not much.)

> This is not to be mistaken for saying it doesn't exist or that it's all in someone's head - it's more just to say that if someone has depression, they have something that may deserve treatment and sensitivity, but that it's something that we still do not know exactly how to describe or diagnose, and so therefore we will just call it "depression" in the meantime.

I'd say that's pretty much on target. However, biology & biochemistry are proceeding forward at a breakneck pace these days. We do have some understanding of the causes for some kinds of depression, and this understanding seems to be improving significantly each year.

[1] https://en.wikipedia.org/wiki/Diagnostic_and_Statistical_Man...

[stcredzero]

What about correlations with patterns in MRI scans?

[fnordfnordfnord]

MRI's are expensive (in the US). Specialist mental health care is not covered under most standard health insurance plans. How about you just fill out the questionnaire[1], and we'll match you with a nice (newly patented) pill?

[1] http://www.depressedtest.com

See also: Questionable sponsorship of online depression tests.

http://www.policymed.com/2010/02/letters-from-grassley-quest...

[ggchappell]

> What about correlations with patterns in MRI scans?

An excellent question, about which I know absolutely nothing.

Something to keep in mind, though: medical tests & whatnot are only useful insofar as they affect the way we handle treatment. Diagnosing depression really isn't that tough; if someone has a debilitating mood disorder, then it is reasonable to get them some kind of help. (I imagine that, for some of these people, the really hard problem is getting them to figure out they have troubles that the medical establishment can help with.)

So I don't think we need MRIs to tell whether someone is depressed. OTOH, can MRIs tell us what treatments are likely to be successful? That sounds like a very interesting question. Hopefully, someone is looking into it.

[EvanKelly]

There's DSM.

http://en.wikipedia.org/wiki/Diagnostic_and_Statistical_Manu...

Worth a look if you're interested in how mental disorders are diagnosed.

[primitur]

.. in the US, according to rules imposed upon the society by the high priests of Industrialized Mental Health.

Not everyone wants a pill for their un-normal quirks, yo.

[SilentStump]

I studied psych in college a few years back and read about a variety of studies on how individuals with slight-moderate depression respond to certain stimuli. One of the most interesting studies (unrelated to the topic) had to deal with individuals looking into a mirror after failing a task. Individuals with >= slight depression would look themselves in the eyes, while happily ignorant individuals would avoid eye contact with themselves. They attributed this with a depressed person's desire to figure out what is wrong with themselves and internalize the failure, where as the happy people would avoid internalizing the failure.

[stcredzero]

> They attributed this with a depressed person's desire to figure out what is wrong with themselves and internalize the failure, where as the happy people would avoid internalizing the failure.

I've also read that depressed people tend to have a more accurate picture of reality. Basically, happy people are walking Dunning-Kruger cases waiting to happen?

[SilentStump]

I believe I know the study you are referring to and you are sort of right. on a scale of accuracy, slightly depressed people are pretty accurate in self assessments, happy people tend to over exaggerate their abilities, and moderately-severely depressed individuals rate their abilities lower than their actual level. So if the person's average ability was a 5/10, happy people tended to rate themselves a 6/10 and moderately depressed people a 4/10 on average iirc.

Edit: My favorite example of Dunning-Kruger happens to be found in religion. The people that know God the most tend to talk about how little they know God, where as the proselytizers that claim the most to know God, really have no clue about the teachings of christ, mohammed, etc.