Folks, welcome back. This is the final section of our lecture on the burden of depressive disorder. And I'm going to show you the methodology for estimating burden used by the World Health Organization and the Global Burden of Disease Study. So one of the ways that you estimate the burden of disease is to somehow figure out what's called disability weights. How important is a given disease? That's the question. And what we're going to try to do is, we know a disease is important if it kills people, if it's fatal. But what we're going to try to do now is we're going to build a methodology, which lets us incorporate the burden of a non-fatal disease with the burden of a fatal disease. That's the crucial innovation that happened, was done by economists, in about 1995. So here's what we do. We present to an evaluator, a rater, say look we're going to give you $100,000. This will improve the life of a healthy person and make him live longer by one year longer. So that's the money you have. Now, you have that $100,000 which will extend a healthy person's life or the population of 1,000 people, you extend their life by one year. How many years would that program have to extend life of a depressed person to make it worth $100,000? So if you have healthy person the disability weight is zero. That means that there doing fine. If they die, if they're dead their disability weight is one. If a disability weight is 0.5, then that prevention program would have to extend life for two years for a group of people with a disability weight of 0.5 to be worth the same as extending the life of a healthy person by one year. This is a cruel logic. It's basically saying it's more fun if you're healthy and it's worth it to extend a healthy person's life. It's worth more than an unhealthy person's life. And you can see a little bit, get a feeling for this, the disability weight for someone with quadriplegia is 0.9. It's very close to death, 1.0. For blindness it's 0.62 and deafness it's 0.33. For major depressive disorder, and there are different categories of major depressive disorder. I've selected the moderate category, the disability weight is 0.35. So let me just show you the way this weight is estimated. What you do is, you present an evaluator, a vignette like this. What you're telling that evaluator, people with moderate to severe depression experience one or more depressive episodes within a year. They go through permanent feelings of sadness or emptiness, loss of interest or pleasure. These are the symptoms we've been talking about. They have problems eating, sleeping, feel worthless or guilty and may have thoughts of death. So this evaluator is given that vignette. And also vignettes for lots of other diseases like quadriplegia and deafness and blindness and, and that person said now here's the $100,000. Where would you spend that money compared to a healthy person? And this is the vignette used and this is the sort of moderate to severe depression. It develops a disability weight of 0.35. Now I think you can see we can take those disability weights and apply them to data on incidence in the course of depression. So somebody has a depressive episode at the age of 20 and they will live, let's say, to the age of 70. That's 50 years. But that 50 years is compromised by the disability weight of 0.35. If the person died at the age of 20 then they would lose 50 years of life. But a person with depression will lose 50 times 0.35 years of life. That let's us equate, basically, fatal diseases with diseases which are impairing or disabling but not fatal. And when you do that, you can combine epidemiologic data with disability data. And the epidemiologic data has data on incidents and primicity of the disease and also the fatality associated with it. You can put those two together and you get something called a disability adjusted life year. Sounds grandiose, but you can actually calculate all the disability adjusted life years that happened in the world in the year 2000. And you can say, and again some of these are caused by lower respiratory infections which are likely fatal. same for HIV and AIDS. Some of those disability adjusted life years are caused by diseases which tend to be fatal, often fatal. HIV/AIDS, Ischemic heart disease. But some of them are cause by diseases which are not so fatal like unipolar depressive disorder in this table. And what this shows is that in the world as a whole, about 5% of the disability adjusted life years are caused by depressive disorder. When this was first published in 1995, it kind of was a shock. Because what happened is the mental disorders crept much higher to the top. Closer to the top than people would have suspected. And depression just climbed way up. And you can see depression is the third most important cause of disability adjusted life years in the world in 2000. And I listed that in blue there you can see it's ahead of malaria, it's ahead of cerebrovascular disease at 3%. Below that less important cause, in order of importance, I listed in blue other mental disorders. So self inflicted injuries, which includes suicide, is the 21st most important cause of disability adjusted life years with about one and a half percent. And alcohol is about one and a half percent and it shows schizophrenia there and bipolar disorder and so forth. That's in the world as a whole. Now let's look at the developed regions. Remember the developed regions have gone through what we call the epidemiologic transition. So a lot of the infectious diseases of childhood they have actually conquered or eliminated or lowered the importance of. So this is what it looks like. You can see Ischemic heart disease has crept to the top now. These are the chronic fatal diseases in the developed region which are more important. And depression is the second most important cause of disability adjusted life years. Alcohol disorders is now the fourth. So what you can see is, I used to wave this at my dean all the time [LAUGH] to try to make sure he understood the importance of mental disorders. Depression is one of the most important disorders in the world. Including a comparison with all the other possible diseases in the world. And as countries pass through the epidemiologic transition change from low income, less developed countries to developed countries. Depression will creep to the top there in their disability adjusted life years. And this reinforces the importance of depression and the importance of planning facilities and services. And prevention programs for depressive disorder and developing part of an overall strategy for public mental health. So that concludes our presentation on the burden of depression. We can look forward in the future to presentations on risk factors for depression. And then presentations by Professor Tolle and Mochdebi about other factors related to the cultural variation in depression and the services used for depression. Thanks for listening. It's been a pleasure to talk to you about something important to me. And that is the epidemiology and public health aspects of depressive disorder, and I hope you've enjoyed the presentation.
