Full text of Dr. Stephen Ilardi, on: Depression is a Disease of Civilization at TEDxEmory conference.
Listen to the MP3 Audio: Depression is a disease of civilization- Stephen Ilardi at TEDxEmory
I believe depression is one of the most tragically misunderstood words in the entire English language and here’s the problem. Depression has two radically different meanings depending on the context. So in everyday conversation when people say they’re depressed, they use the word depression as a synonym for sadness. It’s the normal human reaction to the slings and arrows of outrageous fortune. In that sense, all of us know the pain of depression.
And yet in a clinical context, depression is shorthand for a devastating illness we refer to it technically as major depressive disorder. This is an illness which robs people of their restorative sleep, robs them of their energy, robs them of their focus, their concentration, their memory, their sex drive, their ability to experience the pleasures of life. For most individuals, it robs them of their ability to love and work and play. It may even rob them of their will to live. And I’ll tell you why.
Because we now know depression lights up the pain circuitry of the brain, to such an extent that most clinically depressed individuals, if you talk to them and they let their guard down, they will tell you as they’ve told me hundreds of times. It’s torment, it’s agony, it’s torture, and many begin to look to death as a welcome means of escape.
Depression is the main driver behind suicide which now claims over one million lives every year worldwide. Now I know what you’re probably thinking at this point. Man, this talk is going to be really depressing. So I am going to give you a friendly little spoiler alert. It’s not. It’s truly not.
Depression – yes, it is a treacherous foe. But what I found in my 20 years of clinical research and clinical work is this is a foe that can be defeated. That’s the good news, and that’s the news that I am going to focus on for most of the talk tonight.
First, a little more bad news. Depression is now a global epidemic. In fact, if we look in the U.S. we now find that nearly one in four Americans will experience that agonizing debilitating pain of depressive illness by the time they reach age 75. And it gets worse. The rate of depression seems to be increasing generation after generation. So every successive birth cohort is having higher rates of depression than the one that preceded it.
Now I want you to look at these lines. We’ve got four different generations on this graph. The green line on the right, that’s the oldest Americans and by the time they’ve made it out into their 60s and 70s they have a lifetime rate of depression of 10%. That’s horrible but it’s much lower than every succeeding generation.
Now take a look at the line that really upsets me the most is the one on the far left: that’s our youngest American adults. Do you see what’s happened? By the time they are in their mid-20s they already have a rate of depression up 25%. Remember, we’re talking about a potentially lethal debilitating illness. Left unchecked, it’s an illness that can cause brain damage. And if we extrapolate that line, by the time they reach middle-age, their lifetime rate of depression will already be over 50%.
So what in the world is going on? What’s driving the epidemic? What can we do about it? What causes depression?
Well, on one level when we ask this question, we’re going to face the answer – it’s really complicated. There have been literally thousands upon thousands of published studies that have identified a dizzying array of factors that are implicated in the onset of depression: biological, psychological, cultural, social, behavioural but if we wade through this complexity what we begin to find is there’s a common underlying pathway, a primary driver, a primary trigger, I call it, the brain’s runaway stress response.
Now we all know the stress response. We think of it probably as the fight-or-flight response in its most extreme form. I want you to think about that response and especially how it was evolved and adapted to serve us.
The fight-or-flight response was designed primarily to aid our ancestors when they faced predators, other physical dangers, that required what? Intense physical activity that would go on for a few seconds, for a few minutes, maybe in extreme cases for a few hours. It’s a very costly response but fine if it shut off when it’s supposed to.
Here is the problem. For many Americans, Europeans and people throughout the Western world, the stress response goes on for weeks and months and even years at a time and when it does that, it’s incredibly toxic to the body and to the brain. It’s disruptive to neural circuits in the brain that use neurochemicals you’ve heard of, like dopamine and serotonin, acetylcholine, glutamate and this destruction can lead directly to depressive illness.
It also can actually damage the brain when left unchecked over time, especially in regions like the hippocampus which is involved in memory consolidation and a frontal cortex. And it also triggers an inflammatory reaction throughout the body and brain.
And here is what we’ve learned about depression. The inflamed brain is a depressed brain. Now this is really intriguing because epidemiologists have now identified a number – a big consolation of illnesses that are rampant and epidemic throughout the entire developed world. You can see the list: atherosclerosis, diabetes, obesity, allergies, asthma and many forms of cancer. These are all inflammatory illnesses. They’re all illnesses that are epidemic in the industrialized modernized world and largely non-existent among modern day aboriginal groups.
I believe we need to add depression: clinical depression to this list. It shows all the hallmarks of being a disease of civilization. And you know what that means? It’s a disease of lifestyle.
So consider the experience of the Kaluli people, of the Highlands of Papua New Guinea. They’ve been studied extensively by the anthropologist Edward Schieffelin. He spent over a decade among the Kaluli. One of his research questions was: How often do the Kaluli experience the same kind of mental illness that we do, and he certainly found some forms of it. He interviewed over 2,000 members of the Kaluli and extensively queried them for their experience of clinical depression.
And you know what he found? One marginal case out of 2000. That gives them a rate of clinical depression that’s probably about 100 times lower than ours. I will tell you why I find that really remarkable.
Because among other things, the Kaluli lead really, really hard lives. Really. They have high rates of infant mortality. They have high rates of parasitic infection. They have high rates of violent death. But they don’t become clinically depressed. They grieve absolutely. They don’t get shut down.
What’s protecting them? Lifestyle. Specifically, the Kaluli live a lifestyle very similar to that of our ancestors over the entire Pleistocene epoch that lasted for 1.8 million years.
Did you know that 99.9% of the human and pre-human experience was lived in hunter-gatherer context. So what does that mean? Most of the selection pressures that have sculpted and shaped our genomes are Pleistocene. We’re still really well adapted for that sort of environment and that sort of lifestyle. I’m not saying there hasn’t been any change since then, because of course 10,000 to 12,000 years ago, we had the invention of agriculture. And there has been some genetic selection over that period of time that’s been more minor.