So I'd like to now move to just talking about the epidemiology of schizophrenia.
How often does it occur,
where does it occur, when is the age of onset.
Some of that kind of classic characteristics of the disorder.
We know that schizophrenia is prevalent at
a level of about a half to one percent in North America.
That's typically been the prevalence data that you will see.
So it's a relatively common disorder.
It's clear that it occurs in all cultures and all socioeconomic groups.
Although there is evidence,
that certain cultural groups may have
higher rates than other cultural groups and we'll get to that later.
And the peak onset in schizophrenia is,
for men is in the area of 15 to 25 years,
but the peak onset for women is between the ages of 25 to 35 years.
So there's a real difference in gender expression.
We'll talk about that a little bit in a minute.
It's currently thought that the prevalence among men is higher than women.
Somewhat higher than women and certainly people
like myself who've done studies with people with schizophrenia,
find that they generally recruit people with schizophrenia in
a two-to-one ratio to their studies in men versus women.
Other things that are important to realize about schizophrenia,
is it's a extremely debilitating disease
and creates great stress for the person who suffers from it.
In fact, there's evidence that 50 percent of people with the disorder,
attempt suicide at one point in their life and 10 percent actually succeeds.
These are very high rates of suicide,
giving a sense of how stressful and overwhelming
the psychotic experiences are for the people who suffer them.
The direct costs of schizophrenia,
are about 0.4 percent of the gross national product in the U.S. and the indirect costs,
an indirect cost would be not only the costs included in direct costs,
which are things like direct medical care.
Indirect costs might include,
the years of lost employment with the disorder for example.
Indirect costs, actually make up 1.6
percent of the entire gross national product in the U.S.
So these are really high numbers and show you just how disabling schizophrenia is.
The World Health Organization now places schizophrenia within
the top 10 forms of disability around the world.
So it shows you how disabling the disorder is and how important it
is for us to learn more about the disorder and develop new treatments.
In thinking about the disorder,
one thing that's very important to realize is that there are gender differences.
And as I mentioned already,
the peak age of onset of women tends to be about 10 years later than it is for men.
We know that women are more likely to have a relative with the disorder,
they're more likely to experience positive symptoms which I'll define in a minute.
And they tend to have a better treatment response than men.
Their outcome tends to be better.
Men tend to have what are called negative symptoms,
they have an earlier onset of
the disorder and they tend to have a worse long term outcome.
So what about the etiology or cause of schizophrenia?
Alright, what causes the disorder?
Well, one of the most important findings in the field of schizophrenia,
that has lent a lot of credence to the idea that schizophrenia is a biological condition,
has been revealed through genetic studies.
And these are specifically studies of twins,
studies of first degree relatives and adoption studies.
And what these studies have allowed us to do,
is to understand more about the way in which
schizophrenia may reflect in some way a genetic transmission.
So if we look at sort of the rates of schizophrenia,
as we said in the general population,
the chances of developing schizophrenia are about one half to one percent.
However, if we have a relative,
first degree relative with schizophrenia,
a mother or father with schizophrenia,
a brother or sister with schizophrenia,
our rates jumped to a 10 percent probability of developing the disorder.
It's still very likely that you won't develop the disorder if you have a relative,
an immediate first degree relative.
But your rates have vastly increased,
suggesting that there may be some role of genes in the emergence of the disorder.
We also know from studies of identical twins right,
these are twins who actually share the same genetic material,
that the rates of concordance and when I say concordance,
I mean the probability that if one member of the identical twins has the disorder,
the other one will develop it,
is as high as 50 percent in some studies suggesting
a very strong relationship between
having same genetic makeup an emergence of the disorder.
At the same time,
it's important to realize that people with identical genetic material,
50 percent of the time,
one person gets the disorder,
one of the twins gets a disorder and the other twin does not.
So that also suggests that there must be additional factors in the environment.
And this has led people to what's been called the
diathesis stress model of schizophrenia.
The diathesis is that you have a predisposition,
presumably a genetic predisposition on the one hand,
but then there is stress in the environment which must occur subsequently,
to sort of reveal the effects of these genes and cause the emergence of the disorder.
So it's an interaction of genes on the one hand,
environment on the other.
When we think about schizophrenia and if you look in the slide here,
you'll see that we think of schizophrenia
emerging as a result of a genetic predisposition.
Right, there's a certain set of genes that make it perhaps
more likely that you will develop the disorder.
There are other stresses,
environmental stresses and some of these environmental stresses are
thought to involve actual prenatal stress.
It's a stress around the time of birth or before birth.
So probably one of the best examples of this,
was a study that was conducted of children born to
mothers who suffered through the Hunger Winter in Holland in the early 1940s.
In the early 1940s,
during the Second World War,
the Nazis blockaded Holland from acquiring any kind of food,
they used their Navy to keep any food from coming into the country.
And this was a punishment that the Nazis were doing to Holland
for resisting the Nazi occupation.
And during this winter, this Hunger Winter,
people were really limited in the food that they had access to.
So their normal diet was changed dramatically,
they were reduced to living on very small amounts of food.
And this obviously caused a great amount of stress to the population.
Studies of women who were pregnant at that time,
revealed that after the hunger winter,
so looking at 20 to 30 years out,
after these children were born from these pregnant women,
that the rates of schizophrenia were markedly higher.
That is the development of schizophrenia in the teens, and 20s,
and 30s from women who had undergone the stress of the hunger winter,
were much much higher and this led to the idea that
maternal stress during pregnancy
may in fact play a very important role in the emergence of the disorder.
Obstetric complications had been tied to higher rates of development of schizophrenia,
so that's also important to realize.
And maternal viral infection during different trimesters of pregnancy,
have also been shown to lead to higher rates
of schizophrenia subsequently in the children who were born.
We know that schizophrenia is characterized by cognitive impairments,
by social impairments, and we know that it
has a very episodic course that it waxes and wanes.
The symptoms get worse and then they get better.