Why is depression a risk factor for other diseases and why is it progressive?
While these seem like separate questions, the new mind-body science suggests that they are actually variations on a theme. Depression, in our view, is linked to most other modern illnesses because it shares an underlying pathophysiology with them.18,28 Millions of years of evolution favored the development and retention of extremely robust stress and inflammatory danger pathways. When death and destruction lurked around every corner, the safest policy was to fire off one’s danger pathways first and ask questions later. What did it matter if body and brain tissues were damaged a little each time these pathways activated if this kept one alive for today (an idea that has been popularized as allostatic load).29 No need to worry about heart disease, cancer, or dementia if you were likely to die of infection by age 30.

Consider our plight today, however. The boss no longer rips your arm off when he shouts at you, and many of the jobs once done by inflammation have been farmed out to sanitation and modern medicine. But the old danger pathways just go on firing off every time someone looks at us sideways. The more they fire off, the more damage accumulates. When this occurs in the arteries, it is vascular disease30; when it promotes insulin resistance, it is diabetes30; and when it disrupts glial cell integrity and disorganizes neuronal signaling, it manifests as depression.31,32 Given enough time, the damage usually accumulates everywhere—hence the high comorbidity between depression and most other major modern maladies.

Why is remission so important?
The new mind-body science suggests that depressive symptoms are a “shout out” that the brain and body are in a state that is inimical to optimal functioning and health in the modern world. Conversely, an implication of the ideas presented here is that depressive symptoms are not likely to improve unless a person’s underlying danger pathway functioning normalizes, at least to some degree.28,33 So remission is the best indicator we currently have that a person’s underlying physiology has returned to a safer state. Of course, symptoms are not perfect. If they were, remission would heal all ills.34 In fact, we know that even when remission is achieved, patients remain at greatly increased risk for sinking again into depression when compared with those who have never suffered depression.35

Join us next month as we apply the implications of recent scientific advances to the practicalities of diagnosing and treating depression.
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