Old news: There is a depression epidemic.
Most nearly everyone agrees about the basic fact of an epidemic of depression. Our best numbers from population studies say that nearly twenty percent of people will have serious, clinical depression over the course of a lifetime, with 8-9 percent of adults depressed in any one year period. If you walk in any neighborhood in America, odds are that you will only need to knock on a few doors before finding a household that contains a person who has suffered from depression. Depression is already the most disabling health condition for adults between the ages of 15-44. It is not easy to quantify the harms done by health conditions but our best estimates -- like the World Health Organization's global burden of disease study -- project that depression's carnage will only continue. An ominous straw in the wind, rates of depression are especially high in adolescents and young adults.
Mystery: More depressed people or sicker depressed people?
The simplest explanation for a growing depression toll is that depression is becoming more prevalent in the population. As more people have first onsets and enter the pool of depressed people, the more people can be depressed at any one moment, and the more people who can be disabled by severe, incapacitating episodes of depression. In this view, depression itself has not changed. It's the same old devil, now affecting more people.
Another possibility, argued by Robert Whitaker, in Anatomy of an Epidemic, is that there is not just more depression but worse depression. Has the long term course of the typical depression case worsened over the last 50 years?
Some evidence points to yes. For example, contrast an epidemiological review by Guze and Robins, which concluded that 50% of those initially hospitalized for depression could expect to have zero additional depressive episodes over a 10 year period, with a study 20 years later that found only 20-30 percent of a treated sample gets well and stays well over an 18 month period.
Indeed, Whitaker finds a shift in summary bottom-line statements about the epidemiology of depression. Up to the 1970s the consensus view was that depression was a self-limiting condition, with acute episodes typically followed by full recovery. The much bleaker recent consensus is that depression is chronic, typically involves multiple episodes, and imposes an ongoing symptom burden between episodes.
The possibility that the typical course of depression is worsening is unsettling. Some psychiatrists resist the idea that depression is worsening. They argue that it's been the same old devil all along but we missed it because our earlier studies were flawed in how they measured and classified depression (for example, if you have a stricter standard of recovery fewer people will be classified as recovered).
However, there is other data besides outcome studies that point to depression worsening. Specifically, Whitaker mines the rising number of federal disability claims (SSI and SSDI payments). In 1987, 1 of 184 Americans were on SSI and SSDI for mental conditions. Twenty years later, it's 1 of 76 Americans. Affective disorders are a particularly strong growth area for disability claims. Nearly one and half million Americans are on disability for an affective disorder. Again, particularly ominous, nearly half of 18-26 year olds who are on disability for a mental condition are diagnosed with a mood disorder.
So for a moment let's grant that the growing burden of depression does not simply reflect increased prevalence of depression but increased nastiness of depression.
The obvious next question becomes why.
Bold claim: Chronic exposure to antidepressants worsens the long-term course of depression.
Enter Whitaker with his bold claim: The worsening of the typical long-term depression course is due to the increasing use of antidepressants as the default, first-line treatment!
This claim might strike you as completely off-the wall and outlandish. After all, even if there is a correlation between changes in treatment regimen and outcome (as all first-year psychology students learn), a correlation does not establish causation. Given a few minutes of lead time you could probably generate other candidate reasons for why depression outcomes are deteriorating -- from changes in social structure, to increased stress, even to changing diet or exercise habits. At the same time, it is important to note that the bold claim is not entirely his. Psychiatrists have previously voiced concerns in peer-reviewed journals that antidepressants reduce symptoms in the short-term but worsen symptoms in the long term, building upon the idea of a neuroadaptation.
While I am not ready to board this particular bus, Whitaker does cite several naturalistic studies showing suprisingly good outcomes in unmedicated patients relative to medicated patients. Definitive work here is hard to do because it requires long-term follow up studies with careful control and monitoring of treatment. This work is both expensive and labor-intensive. Pending more definitive data on why the average course of depression may be deteriorating, Anatomy of an Epidemic is important food for thought.
Even if Whitaker's bold claim turns out to be wrong, it is clear that the revolution in pharmacological agents has not ushered in a corresponding revolutionary improvement in depression outcomes.