Why is Depression Incidence Increasing?

A happier time?

As discussed in last week’s post, since 1956 (when the first of the tricyclic antidepressants was released) the rates of depression in the general population have skyrocketed. Depression has become widespread where it was formerly rare, recurrences have become more common, inter-episode recovery has declined, and long-term disability has increased.

Some of these changes can be argued about to an extent. Some cases may not have been found in the 1950s. Chronicity may have been inadequately monitored or reported. The lack of disability insurance may have forced the disabled into work, or into the back bedroom of the house, where they might go uncounted.

These and related observations might account for the apparent rise of depression if the numbers were in any way similar, but they are not. Estimates of depression prevalence are between 10 and 1000 times as high today as they were in the 1950s. No failure of measurement can account for an increase that large. Either the disorder is trivial and therefore easily missed (and unnecessary to treat), or it is significant and at least somewhat obvious to caregivers and families.

(Note: Both of those bracketing numbers are extremes – I have seen no reports that would suggest depression is as infrequent as 10 times the 1950s rates, and the upper figure seems to be a comparison of a 1950s-era point prevalence estimate – 100 per million - with the modern lifetime incidence estimate of 10%, or 100,000 per million.)

If you raise this issue at a dinner party, do so with stopwatch in hand. Count the seconds until someone says “Life is so much more stressful now than in the 1950s.” Observe as they sit back, satisfied that the question need be given no further consideration. Even clinicians offer this all-too-pat explanation.

The speed with which we discard the notion that something else might be happening is surprising, and suggests discomfort with the topic. “If I look inside that cave I might find something unpleasant. So let’s just pretend it’s not there.” Mental health services, being so expensive, must be effective. So if depression has increased, it must be due to external forces. If we weren’t trying our best, surely they would be even higher.

Comparing 1956 to 2015

Nostalgia is almost always rose-tinted. A friend once expressed the wish that he lived in 1800s-era England. He was somewhat put out when I suggested that at his present age he would most likely be dead, and that perhaps his imagined version of Dickensian London was overly cheerful.

Rather than trying to compare the present day with the imagined past, let’s consider two concurrent societies: One with the living conditions of 2015, and a bordering nation with the conditions of 1956. In this thought experiment we will assume that dispassionate aliens have just landed, and we present them with a task: Examine the conditions of each society, then guess which one has the higher rate of clinical depression. For argument’s sake, I’ll use Canadian data for the example.

• Life expectancy. 1956: 68; 2015: 80. Living on one side of the border confers an average of 12 additional years of life.
• Income.  Higher in 2015 than 1956, adjusted for inflation, with a vastly increased array of products and entertainments available.
• Recent war. 1956 is 12 years out of a world war that traumatized much of the population; there are significant fears of an impending nuclear exchange. 2015 has a recent military commitment in Afghanistan participated in by a far smaller proportion of the population.
• Universal healthcare. 1956: Not in most provinces; illness runs a significant risk of bankrupting a family. 2015: Yes, plus extended health benefits available through most employers.
• Childhood mortality. 1956 32.6/1000 (from 1956-1960 data); 2015: 6.1/1000 (estimate from 2011 data). Children in 1956 routinely die from a multitude of communicable diseases ranging from diphtheria to polio. Parents suffer realistic fears that one or more of their children will not reach adulthood. In 2015, fears of communicable illness have waned sufficiently that many give more attention to discredited concerns about vaccines, and see little reason to have their children vaccinated.
• Status of nonwhite, nonheterosexual, disabled, and female populations. Varies by group, but in virtually all cases worse in 1956 than 2015.

This is, admittedly, a highly selective set of factors on which to compare two cultures. It would be easy to generate dozens more, and on some of them 1956 would do better than 2015. Insert any variables you like.

Then pose the question to the observers: “Which of these two cultures would you guess has the higher rate of clinical depression?” 

Once we set aside nostalgia, it’s difficult to escape the conclusion that 1956 should have a somewhat higher incidence than 2015.

Perhaps you disagree, feeling that the two might be judged equal once all positives and negatives are tallied, or that 2015, with its environmental concerns and focus on terrorism, would be judged the harsher world. Fine. But would our impartial observers conclude that the rate of depression should be 10 times as high on one side of our hypothetical border than the other? A hundred times? Unlikely.

Something else must surely be going on, for our efforts to conquer depression have failed this badly.

Treatment Penetration

Another explanation that is frequently offered for the increase in depression in our culture is that too few sufferers seek help. Only half of people with depression tell their doctor, so this myth goes, and only half of those are given treatment.

This is nonsense.

More Americans currently take antidepressant medication (11%) than are thought likely to have a major depressive episode in their lifetime (10% by most estimates). Figures in Canada and other developed economies are similar. “From 1988-94 to 2005-08, the rate of antidepressant use in the United States among all ages increased nearly 400%” (Pratt, Brody, & Gu, 2011). One study found that 19% of British Columbia women were prescribed an antidepressant in 2003.

The problem is clearly not the failure of antidepressant treatment to reach those who need it. Indeed, over-prescription appears to be a significantly greater problem than under-prescription.

So what’s happening?

It’s not entirely clear at this time why depression rates have risen so dramatically. In all likelihood, there are multiple factors at play.

One possibility raised by many – and summarized by Robert Whitaker, in his book Anatomy of an Epidemic - is that pharmacological treatment itself may be one of the prime culprits, despite clearly helping some of the people who take it.

This line of reasoning contrasts short-term improvement (which is usually the variable examined in medication outcome trials) with long-term outcomes (such as chronicity, recurrence, and disability). The latter are examined much less often than the former. We have tended to assume that short-term gains predict sunny long-term outcomes, but it turns out that this may not be the case. More on this in another post.

Reference

Pratt, LA, Brody, DJ, & Gu, Q (2011) Antidepressant use in persons aged 12 and over: United States, 2005-2008. National Center for Health Statistics Data Brief, Number 76, October 2011.

Whitaker, R. (2010). Anatomy of an epidemic. New York: Crown.

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