The psychosis in African and

Caribbean origin populations

Prof Kwame McKenzie MD

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Searching for answers for my

patients

Is

schizophrenia

more common

in Black

people?

If so why?

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African and Caribbean origin

populations

Third largest visible minority in Toronto in 2006.

352,200 people

16.2% of Toronto's visible minority population,

6.9% of its total population.

55.4% of the Black population are foreign-born

of those who are foreign born 55.1% came from either

Jamaica, Trinidad and Tobago, or Ghana.

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African and Caribbean origin

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Schizophrenia and psychosis

0.5 -1% risk in lifetime

Costs billions to Canada but main impact on

individuals and families

Symptoms – delusions, hallucinations, problems

with control of thought, social withdrawal, cognitive

impairment, depression

often starts in teenage years

30% symptomatic recovery

Majority not working

Die 25 – 30 years younger

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Meta-analysis – schizophrenia

incidence Selten & Cantor Graae Am J Psychiatry. 2005 Jan;162(1):12-24.

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Migrants risk of schizophrenia Selten & Cantor Graae Am J Psychiatry. 2005 Jan;162(1):12-24.

Migrant group Relative risk 95% CI

first generation 2.7 2.3-3.2

second generation 4.7 1.5-13.1

“black” migrants 4.8 3.7-6.2

“white” migrants 2.3 1.7-2.9

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Two camps

Biological Social

Professional view Community

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Biological camp

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Genetics – highly heritable

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Obstetrics

Obstetric problems common

Non specific risk factor with small impact on schizophrenia risk

Hypoxia before or during birth may impact on brain development increasing risk of later schizophrenia

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Obstetrics

Winter and spring births more likely to develop schizophrenia

could be due to viral infection or vitamin D

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Swedish study

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Cannabis:

analysis of best studies

Cannabis 2X increase individual’s risk for later

schizophrenia

Elimination of cannabis use would reduce the

population incidence of schizophrenia by 8%,

But cannabis neither a sufficient nor a necessary

cause for psychosis.

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Biological theory: changes

in structure

Biological insult to the developing brain leads to problems later on.

Decrease in grey matter, enlargement of ventricles, focal alteration of white matter

Pathways of neuro-transmitter dopamine in the limbic system and parts of the pre-frontal cortex involved

Increase in dopamine synthesis, dopamine release, and synaptic dopamine

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Social camp

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Childhood

Social factors increase the risk of developing

schizophrenia:

Separation from parents for more than a year in

childhood

Social adversity in childhood (more adversity more

risk)

Psychological trauma / Bullying / poverty

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Stress important

Increased risk of schizophrenia if you…

Live in neighborhoods that are stressful

Have numerous daily hassles

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Racism risk factor for

psychosis

Estimated prevalence of psychosisEstimated prevalence of psychosis

All Ethnic Minority Groups

0.0%

1.0%

2.0%

3.0%

4.0%

No Verbal

only*

Physical* No Some Most*

Racial harassment British employers discriminate

Karlsenn et al Psychological Medicine 2005 Sept 29-1-9

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Urban environment

Increased rates of psychosis in

cities not due to drift alone

Being born and brought up in a

city are risk factors.

The risk increases as the size

of the city increases.

Longer you live in a city when

you are young, the higher your

risk for developing psychosis

22

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Social model

Schizophrenia result of trauma and stress

The more social stress, the higher the risk

Problematic psychological mechanisms may start

in childhood

Adult stress on top of childhood mechanisms

leads to psychosis

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Genetic risk amplifies biological

and social risk

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25

0

10

20

30

40

50

60

70

80

Social cohesion and trust (ward-level)

Pre

dic

ted

inci

den

ce r

ate

(per

100

,000

per

son

-yea

rs)

White

BME

Low Medium High

Incidence of psychosis by ethnicity

and social cohesion

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A new science

Mind not the Brain

Epi-genetics not genetics

Social impacts on biological mechanisms

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How does all this cause mental illness

Mental illness lies in the biological and

psychological mechanisms that adapt us to the

environment

Symptoms are behaviors and thoughts that

reflect body trying to adapt

Illness reflects differential acceptance by society

of different types of adaptation

Our biology and psychology are linked

processes in adaptation

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Biological development

depends on the environment

Development of brain and mind depend on

environmental stimulation

Normal development of neuronal connectivity

depends on impacts of environment during

sensitive periods of development

Different psychological processes develop at

different times

Mechanisms that build resilience are developed

through interaction with the environment

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Molecular function mediates our

response to environment

Epi-genetics = reversible regulation of various genomic functions, occurring independently of DNA sequence,

Mediated through changes in DNA, eg. methylation and chromatin structure.

Help us develop and regulate gene function

They regulate genetic our response to environmental stimuli such as stress

Other candidates – neurogenesis and inflammation

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Early adversity may have long

term impacts

Early neglect and other environmental insults

impact stress signaling.

Causes impaired neuronal responsiveness in the

meso-limbic system and symptoms of pre-frontal

cortical dysfunction

Makes you more sensitive to stress and more likely

to produce sub-clinical psychotic symptoms

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Trajectory then mediated by

social world

Psychotic symptoms in adolescence transient and

sub-clinical

But repeated exposure to stress triggers persistent

and more severe symptoms

Social response to symptoms may cause chronicity

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Why high rates in black populations

Increased biological risk factors

Genetics in second generation

Access to obstetric care

Increased social risk factors

Separation from parents increased

Social adversity in childhood

Increased daily hassles and stress because of SES and racism

Increased urban birth and residence

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Answers for my patients

Causes of psychosis are multi-level – no one person or one thing causes psychosis

Neither patients or parents are to blame

Social and biological are linked

Problems is mind not the brain

Focusing on the mechanisms that lead to adaptation to stress and trauma offers a chance of cure as well as prevention

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Thank you