So now, I think I showed
you earlier that when we want to study
the force of morbidity we need an incidence study.
And to do an incidence study, we have to have a
perspective study where we interview people at one point in time.
And we determine that there are some people who are at
risk for the first onset of a given disease or disorder.
And, of those risk set people, what percentage of them, or
what rate of onset is there.
And so to do an incidence study, and study incidence over time, is very difficult.
In fact there are only three studies in the world that I can
find that are based in the population that actually let us do this.
This chart has them placed there, so we have the study in Lundby, Sweden.
you can see the, the left hand most black diamond there which is about
2.3 on the left axis there.
The annual incidence is about 2.3 per 1,000 per year.
And that is a study conducted between 1947 when the
risks that was established in a small town Sweden in 1957.
And the follow up when the incidence rate
was established, so that's the left most black diamond.
And then from 1957 they established another
risk set in that same population, and
followed up in 1975 that's the second life time.
And so actually to make a trend in depressive disorder, you need
three points in time, each incidence rate requires two points in time.
You can see.
And this is the study in Lundby is the one led by Ula Hagnel who wrote the
article after looking at this data, these black
diamonds, saying are we entering an age of melancholy?
Because it seemed to show that
the rate of incidence of depressive disorder went from 2.3 to 4.5.
And so we only have two other studies that can do this.
One of these studies is in Atlantic, Canada.
And again this is a three wave study.
They start in 1952 and then followed up through 1970.
And looked and established all the new cases of depressive disorder, divided by
the personal years of observation, and then you've got a rate of 4.5
per 1,000.
Then they did this again from 1970 to 1992, 22 years.
And their rate was more like 3.8 per 1,000.
Finally the third study is the Baltimore ECA project which I was leading, and there
was a study in 1981 to 1993, and the incidence rate was three per 1,000.
You can see these incidence rates are not too far off,
even though they're in very different areas.
The incidence of depression is kind of close.
And when we follow that group through 2004, the new cases
of depression produced an incidence rate of about two per 1,000.
So, we have Hagnel's work in Lundby, Sweden, with a sharp rise from 47 to 75,
and then the study in Atlantic Canada by Jane Murphy in Collaborators
showing a decline, and then the Baltimore, Maryland study showing decline.
So we conclude, the data does not suggest a rise
in the incidence of depressive disorder with the passage of time.