Say that in the current financial turmoil you lose your job or your nest egg and respond by manifesting the signs and experiencing the symptoms of a depressive disorder: are you depressed? Yes, very likely you are, according to the way doctors currently diagnose mood disorder. No, say certain critics who believe that most “caused depressions” are better understood as mere sadness. But the naysayers’ case took a terrible blow this past month, in the form of a study that examines the varieties of grief.

For the research, Kenneth Kendler, a psychiatrist and perhaps our leading behavioral geneticist, joined Sidney Zisook, author of an important paper on the use of antidepressants to treat grief-related depressive symptoms. The team looked at the relationship among normal grief, apparent depression arising from bereavement, and diagnosable depression arising from other stressors.

The findings are finally too detailed to be conveyed in a brief summary, but the researchers arrive at what in the scientific literature counts as a forceful conclusion: “[B]oth this study and our recent literature reviews suggest that bereavement-related depression is probably similar to other forms of major depression. Bereavement-related depression is recurrent, genetically influenced, impairing, and treatment-responsive. These are all characteristics that are more likely to be associated with major depression than ‘normal sadness.’”

Looking at members of twin pairs, the researchers examined 82 subjects whose depressive symptoms arose in response to loss of a loved one and 224 subjects whose depression related to other stressors. There were some differences, but the between-group similarities were much more striking.

In particular, when compared to subjects with stress-associated depression, people with grief-driven depression had the same age of onset, the same number of prior episodes, the same indicators of risk for future episodes, and — get this! — the same risk of depression in a co-twin. Even those depressed-and-bereaved subjects who met criteria for “normal grief” had the same heightened level of depression in co-twins. That is to say, people who respond to bereavement with depression are subject to the same genetic risk that drives depression altogether. Those subjects whose episodes looked like “normal grief” (with a short duration and lack of suicidality), also looked — simply depressed.

This study is not utterly conclusive, but a fair reading says that it casts a deep shadow on an argument that’s gotten altogether too much press. Readers of this blog will recall that the theorists Allan Horwitz and Jerome Wakefield champion a line of reasoning that runs like this: In defining depression, psychiatry makes an exception for normal bereavement. If you’re in grief, even if your grief has all the symptoms of depression, you’re not depressed. Why not make a similar exception for any stressor, so that if your grief arises from divorce, you’re considered merely sad?

Those interested in a thoroughgoing answer to this challenge, should look at an address on the subject that I gave at Rutgers University. In part, I said, “In behavioral genetics, where it is critical to distinguish subtle signals from loud noise, researchers tend not to exclude bereavement. If stress triggers depression, the result is counted as depression. The character of the stress is irrelevant.” The data is simply more consistent — you stand more of a chance of finding relevant genes — if you count grief-related depression as depression.

The current Kendler-Zisook study justifies this practice. The authors conclude: “These results question the validity of the bereavement exclusion for the diagnosis of major depression.” That was the result I (and many others) had predicted. In part because there are a few distinctive features of bereavement, but mostly for political reasons — expanding depression to include depressive forms of bereavement simply makes people uncomfortable — the bereavement exclusion will likely linger on in the diagnostic manuals. But when scientists are being frank, they say that there is no paradox: stress-triggered depression is depression, conveying all the risk of depression, from suicide to heart disease to recurrent episodes. Bereavement acts like other stressors, bringing forth a dangerous syndrome in those who are vulnerable on the basis of genetics or prior experience.

Ronald Pies, my former colleague on the Psychiatric Times and now its editor (congratulations, Ron!), gives a mild rejoinder to Wakefield and Horwitz in today’s Science Times. I wish that Pies had included this new finding from behavioral genetics. The “mere sadness” hypothesis was already shaky on any number of grounds. This new research knocks the legs out from under the one argument that was distinctive. Yes, the Kendler-Zisook study says, the response to bereavement does often look like depression — because bereavement often results in depression.