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Dr. Kwame McKenzie - Psychosis in Black Populations
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Dr. Kwame McKenzie - Psychosis in Black Populations


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  • 1. The psychosis in African andCaribbean origin populationsProf Kwame McKenzie MD
  • 2. Searching for answers for my patients  Is schizophrenia more common in Black people?  If so why?+
  • 3. African and Caribbean origin populations  Third largest visible minority in Toronto in 2006.  352,200 people  16.2% of Torontos 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.+
  • 4. +
  • 5. African and Caribbean origin+
  • 6. 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
  • 7. Meta-analysis – schizophrenia incidence . Selten & Cantor Graae Am J Psychiatry. 2005 Jan;162(1):12-24+
  • 8. Migrants risk of schizophrenia . Selten & Cantor Graae Am J Psychiatry. 2005 Jan;162(1):12-24Migrant group Relative risk 95% CIfirst generation 2.7 2.3-3.2second generation 4.7 1.5-13.1“black” migrants+ 4.8 3.7-6.2“white” migrants 2.3 1.7-2.9
  • 9. Two camps+  Biological Social  Professional view Community
  • 10. Biological camp+
  • 11. Genetics – highly heritable+
  • 12. 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+
  • 13. Obstetrics+  Winter and spring births more likely to develop schizophrenia  could be due to viral infection or vitamin D
  • 14. Swedish study+
  • 15. 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.+
  • 16. 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
  • 17. +
  • 18. Social camp+
  • 19. 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+
  • 20. Stress important  Increased risk of schizophrenia if you…  Live in neighborhoods that are stressful  Have numerous daily hassles+
  • 21. Racism risk factor for psychosis Estimated prevalence of psychosis All Ethnic Minority Groups 4.0% 3.0% 2.0%+ 1.0% 0.0% No Verbal Physical* No Some Most* only* Racial harassment British employers discriminate  Karlsenn et al Psychological Medicine 2005 Sept 29-1-9
  • 22. 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
  • 23. 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+
  • 24. Genetic risk amplifies biological and social risk+
  • 25. Incidence of psychosis by ethnicity and social cohesion 80 Predicted incidence rate (per 100,000 70 60 person-years) 50 40 White BME 30 20+ 10 0 Low Medium High Social cohesion and trust (ward-level) 25
  • 26. A new science  Mind not the Brain  Epi-genetics not genetics  Social impacts on biological mechanisms+
  • 27. 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
  • 28. 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
  • 29. 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
  • 30. 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+
  • 31. 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+
  • 32. 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
  • 33. 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
  • 34. Thank you+