Folks welcome back, this is Section C, lecture on the burden of depressive disorder, and this section we're going to talk about the Natural History of Major Depressive Disorder. It means really the course of depressive disorder. Once it starts, what happens? And the natural history includes several different terms, these are terms in Clinical lore. But also in public health discussion. So the prodrome is the period after the disease has begun but before its diagnosed. [UNKNOWN] disease has you might call it an occult property, and prodrome is very difficult t, to find because eh, you see somebody who you think might have the so called disease or depressive disorder. But then it doesn't start. And so if it doesn't start it wasn't there so, so, the prodrome wasn't there. But sometimes, the disease, once it gets to a certain point, it proceeds inevitably, it's inelluctable. That means the prodrome has started. The prodrome is very hard to observe. I'll show you but it's very hard to actually decide when it starts for a given individual. Onset is easy, it's the beginning of the first episode. Remission is when the symptoms in a given episode stop. Recovery is a little trickier. Recovery occurs when, and this is a, a definition that the folks that study depression have taken. After a year has passed without another episode of depression, we say they have recovered. We wait a year before deciding that the recovery is there. And then after a recovery, we can have another episodes, that's recurrent episode. So now here's the prodrome of major depressive disorder and the way we assess this prodrome is we have, in this case, 148 new cases of depressive disorder in the Epidemiologic Catchmentary Program. And, for each of those new cases, there are a series of questions says listen, you've told us about being sad and you've had appetite problems, and sleep problems, and fatigue, and concentration when you were sad during that two week period. When you were depressed, what did you first have a problem like that? And eh, what turns out they don't say it was last week or last month, tend to say eh, was, when I was 17 and their 35. So, what this shows is these are cumulative percent with onset. And the Onset of Disorder, if you look at the horizontal line 60, you can see that by age 45 about 60% of the onset of depressive disorder in that population will have occurred. Okay by age 45. But those people at age 45 when you ask then when it started, they will say about 20 years ago. And that's the onset of the problem, so the, the space between those curves is you might call a Prodromal Period, that's an estimate of a prodromal period. And the point is, for depressive disorders and for lots of other mental and behavioral disorders, prodromes are long the whole thing is slow. This is another angle on the prodrome, now instead of asking people, well when did you ever have problems like that. These are the 71 new cases that I showed you earlier. We asked them, when did you have a period of sadness for two weeks or more, that's Dysphoria. Or when did you have problems with Appetite for two weeks or more during a period of being sad. And so, we have the nine criteria here, this is in a way to remind you of the criteria sadness, loss of interest to appetite sleep and so fourth and suicidal indication. And these are box plots. This is called a horizontal box plot, for what it's worth. And you can see, in the middle of the boxes there or on the left-hand side there's a vertical bar, that vertical bar is 50% of the cases. So, if we just look at appetite, we see that 50% of the people with an onset of depression report onset of appetite problems 2 years or sooner. That is 2 years or less, and 50% report two years or more. Those bars are all about one or 2 years, you can see, for sleep. For slow and restlessness for fatigue and so forth. But there are two exceptions, these are exceptions are non, non trivial exceptions. It's Dysphoria and Suicidal Ideation. So, we see that three quarters of the population have a prodrome involving sadness for 15 years or more. That's, if you look at the row for dysphoria, there were 63 of the 71 new cases included dysphoria as one of their symptoms. Half of them had the dysphoria for 5 years or less, but half of them had it for 5 years or more, that's the vertical bar there. So dysphoria and suicidal ideation, you might say there's psychological aspects of depression. They start early, it's slow and it of course very hard to predict with somebody whose sad, or if they have suicidal or issues. whether they're eventually going to meet the criteria for major depressive disorder but it is true that if they have anhedonia or appetite or sleep problems it's going to be quicker. That's the notion here. Here's recovery from major depressive episode. This is a survival chart, so this is the proportion with a continuing episode. And you can see, we start, there's a 12 year Follow-up. And when the episode ends, if you look at the upper left there, by one there's 100% that are still in the episode, but after 1 year, almost all the folks that were prevalent cases, in 1981 cases have recovered. They've had a year without another episode of depression. And there are new cases there and we can see that for them after 2 years about 50% of them have not recovered yet. The strong drop for the blue bar, those are prevalent cases of depression. And almost all of them have a year without an episode they recover and 1 or 2 or 3 years, but the new cases don't have such a quick recovery. And so we have puzzled over this. We, we don't have a perfect explanation, but I think I know what the explanation is. For this difference between new cases and prevalent cases, and that is, when somebody has an episode of depressive disorder for the first time in their life, they don't really know what it is. They can't figure it out and they're puzzled by it and it takes them a while to get to [LAUGH] a doctor basically and get treated for it. And a prevalent case, sometimes if you talk to somebody who knows they have depressive disorder, they know they have recurrent depressive disorder, they can almost predict when it's going to happen. They predict it's November, the sun's going down. I have to go to Florida or I'm going to get sad or I have to go to the doctor because I'm feeling appetite problems and I need to get a new medication. So folks with prevalent depressive disorder, just like folks with prevalent diabetes, they know how to treat it. Folks that greet it for the first time in their lives, it takes them longer to figure out what to do, and therefore, their recovery is slower. Now, this is after the recovery. We start with on the upper left with a 100% that will not have a Recurrence because, you know, they had a recovery. The question is how long does it take to have a recurrent episode of depressive disorder. And this, you know, the question arises whether depression is a quote chronic disorder or not. And it depends on whether you think if the glass is half-full or half-empty. And half is the actual thing, it's the median right there. You can see that even after 20 years, 50% of the population that have had an episode of depressive disorder and recovered had not had a recurrence. So, that's the non-chronic, that's the glass is half full I guess you can say, it's not a chronic disorder because 50% recover and never had a recurrence. Most people who have had an episode of depressive disorder never have another one, but about 50% do have another one. So here's the Summary of the Symptomatic Course and that is what I've told you. The prodrome can be decades long. Episodes, I didn't show you data on this, they tend to last several months, 3 months let's say. But about 50% of all cases occurring over the lifetime have only one episode, on the other hand, about 15% of episodes are what we might call unremitting. So when we looked in the follow up data for the new cases or the prevalent cases, there were some people basically had an episode of depression every single year. Every year we followed them they had an episode of depression. This is a small proportion, it's 15%. And then about 35% had what you might call a relapsing and remitting course. They have a recovery, they get better, then they have a recurrence, then they have a recovery, then they get better. It's about 30 so, the 50% versus 50 is the glass full, half empty business. Now I want to show you information about gender and depression. And I want to use this to illustrate a little bit the difference between Prevalence and incidence. But the first piece of information is that gender is associated with the prevalence of major depressive disorder. And so, women has twice as much is what it comes down to. And this is f, just for selected studies in the US and Edmonton and Canada and Munich and New Zealand, but basically, almost every study that will show data like this. There's a Lifetime prevalence on the left hand and so, in the US, for example, it's 2.3 versus 1, and 1.76 versus 1 and 3.4 and so, it's 3 and a half times the prevalence in Munich for females as for males, and so fourth. Now that is not true for many other mental disorders. And this is to show you the contrast between Bipolar disorder, which is an effective disorder related to depressive disorder but not the same and you can see prevalence of bipolar disorder is much lower in all four sites. But also and this is a little bit harder to see, that there's no real sex difference between bipolar disorder for males versus females. So depressive disorder is where the sex difference is and females have more. Now this is the interesting explanation in part for the prevalence difference. So this is the relative risk, though. How are the relevant risk, that means if you're male and your risk was one, what will the risk be for a female well, it's 1.98 for becoming a new case of depressive disorder. So it's twice much, and that's about what we saw in terms of prevalence about twice as much, but this is incidence, this is the force of morbidity, remember. Now if we look over at Recurrence. We can see while there is a male, female difference in incidence, there is no difference in recurrence, and there's very little difference in the duration of episodes. So what this means is, if you are a male, you have a lower chance of having an episode of depressive disorder. But once you do, your future course of depressive disorder will be the same as a female. So now we're thinking what is it about femaleness that this is the forcing morbidity incidence, where that produce that pushing females into the category of depressive disorder. So here the explanation is incidence not prevalence. And what this means is that the chronicity of depression is the same for males and females, it's the incidence that's different. So that concludes our study of the prevalence and incidence of depression. I hope it illustrates the principles of prevalence and incidence, as well as giving you information about depressive disorder. We'll turn to an elaboration of the natural history of depressive disorder in section D which is about, medical conditions.
