Causes of Psychosis


My name is Dr. Kwame Mckenzie I am a psychiatrist at the Centre for Addiction
and Mental Health and the University of Toronto. I am here today to talk about the cause
of psychosis. So when people think of the cause of an illness
they always think of something like pneumonia where you get a bug and that bug causes the
illness. But that is not how most illnesses are caused.
Most illnesses you don’t find one single thing that causes the illness. It is more like heart disease. We all know
that you might be at risk of heart disease because of your family. But we also know that whether you get a heart
attack or not depends on the things that happen to you. How much stress you have in your life, how
much exercise you do, whether you smoke, what your diet is like. All of those things are important for your
risk of heart disease. Not a simple cause; your risk of heart disease And of course, what you eat, how much you
exercise and what sort of job you have, depending on where you are. So your risk of heart disease is partly due
to who you are, your genes, but a lot do with what happens to you as you
go along in life. It is not a simple cause, it is things that
happen to you that increase your risk. Schizophrenia is exactly the same as heart
disease you don’t find a single cause for schizophrenia but there are lots of things that increase
your risk. When people are thinking of those things
it will increase your risk. They really put them into two big buckets,
biological and social. When people are thinking about biological,
they are thinking about physical things like your genes or like taking cannabis, that increase your chance of developing a
psychosis. Now we all know that if somebody in your family has been diagnosed with schizophrenia or any
psychosis you are more likely to develop it yourself, but the truth is, most people who develop
psychosis don’t have any clear family of history of psychosis at all. We also all know that some things like taking
cannabis increase your risk of developing psychosis. There are other things that most people
maybe don’t know about. If you have had a difficult birth, so an obstetric
complication that also increases your risk of developing a psychosis later in life. There are these biological factors that
people talk about and obstetric complications, cannabis and
heredity or genes are the things that people generally think are important. There are lots and lots and lots of other
risks but those are the ones that people talk about. Then there are social factors. Social factors
have had a lot of research recently and they have shown us some interesting things. For instance if you life in a city when you’re
young, you have an increased chance of developing a psychosis. If you are separated from your parents before
the age of 15 again you have an increased risk of psychosis. If you are bullied, or you have social adversity
when you are young, you have an increased risk of developing psychosis. And those sorts of social adversities can
also increase your risk of psychosis. If you are older, so if you are a victim of
racism when you are older, if you are unemployed. All of those things
that lead to social stress increase your chance of developing a psychosis. The list is very long of the social factors
that can increase your risk of psychosis. Where the confusion happens is we often see
the thing that happens say for instance, taking the cannabis when
somebody is 16 or 17 we say, well that was the cause. What we don’t see is the vulnerability
is generated earlier. It is never, almost never, one cause it is loads of little risk factors that are
working together to increase your risk of developing a psychosis.

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