1. Schizophrenia: An Evolutionary Perspective By: Tanya Kraus

2. Schizophrenia  a psychotic disorder characterized by major disturbances in thought, emotion, and behaviour – disordered thinking in which ideas are not logically related, faulty perception and attention, flat or inappropriate affect, and bizarre disturbances in motor activity. Patients with schizophrenia often withdraw from people and reality into a fantasy life of delusions and hallucinations.  a psychotic disorder characterized by major disturbances in thought, emotion, and behaviour – disordered thinking in which ideas are not logically related, faulty perception and attention, flat or inappropriate affect, and bizarre disturbances in motor activity. Patients with schizophrenia often withdraw from people and reality into a fantasy life of delusions and hallucinations.

3. Positive/Negative Symptoms Positive symptoms: Involves behaviour that is not normally present in most people. (E.g. distortions, disorganized speech, hallucinations, or delusions.) Positive symptoms: Involves behaviour that is not normally present in most people. (E.g. distortions, disorganized speech, hallucinations, or delusions.) Negative symptoms: Involves behavioural deficits that are not present in most people. (E.g. avolition, alogia, anhedonia, flat affect, and asociality.) Negative symptoms: Involves behavioural deficits that are not present in most people. (E.g. avolition, alogia, anhedonia, flat affect, and asociality.)

4. Other Symptoms Many patients experience the following as well as positive and negative symptoms. Many patients experience the following as well as positive and negative symptoms. Catatonia: Defined by several motor abnormalities, which can include catatonic immobility or waxy flexibility Catatonia: Defined by several motor abnormalities, which can include catatonic immobility or waxy flexibility Inappropriate Affect: Emotional responses that are out of context Inappropriate Affect: Emotional responses that are out of context

5. Here’s Where the Evolution Part Becomes Relevant… Unusual behaviours that strongly resemble schizophrenia have dated back to Mesopotamia Unusual behaviours that strongly resemble schizophrenia have dated back to Mesopotamia Universally, the prevalence rate of schizophrenia is about 1%, which exceeds common mutation rates Universally, the prevalence rate of schizophrenia is about 1%, which exceeds common mutation rates There is a strong genetic component (E.g. twin and adoption studies) There is a strong genetic component (E.g. twin and adoption studies) Conditions such as schizophrenia have a long history and a strong genetic base, meaning evolutionary explanations must be acknowledged Conditions such as schizophrenia have a long history and a strong genetic base, meaning evolutionary explanations must be acknowledged

6. Evolution Perspectives Evolutionary perspectives can be divided into two groups: a) Theories that assume schizophrenia is a disadvantageous by-product of human brain evolution b) Theories that consider schizophrenia to have an evolutionary advantage

7. Schizophrenia: Disadvantageous By- Product of Human Brain Evolution Theory #1: Farley’s argument that schizophrenia could be an extreme variant of normal social behaviour Theory #1: Farley’s argument that schizophrenia could be an extreme variant of normal social behaviour Flaw: This theory fails to explain why schizophrenia is comprised of both negative and positive symptoms Flaw: This theory fails to explain why schizophrenia is comprised of both negative and positive symptoms

8. Disadvantages, Cont. Theory #2: Randall’s novel neural pathways model…”biological trial and error of connection would produce a range of behavioural variants, including schizophrenia.” Theory #2: Randall’s novel neural pathways model…”biological trial and error of connection would produce a range of behavioural variants, including schizophrenia.” Flaw: Denies the specific symptoms that occur in any given disorder, as well as the maintenance of pathology Flaw: Denies the specific symptoms that occur in any given disorder, as well as the maintenance of pathology

9. Disadvantages, Cont. Theory #3: Saugstad’s pathophysiological model, which connects many frontal lobe disorders (E.g. schizophrenia, infantile autism), to delayed cerebral maturation. Again, schizophrenia is viewed simply as an outlier within the normal bounds of variation Theory #3: Saugstad’s pathophysiological model, which connects many frontal lobe disorders (E.g. schizophrenia, infantile autism), to delayed cerebral maturation. Again, schizophrenia is viewed simply as an outlier within the normal bounds of variation Flaw: It would be atypical for nature to produce such large numbers of distinct phenotypes with reduced fecundity (Ability to produce many children) Flaw: It would be atypical for nature to produce such large numbers of distinct phenotypes with reduced fecundity (Ability to produce many children)

10. Disadvantages, Cont. Theory #4: Yeo and the developmental instability model of schizophrenia Theory #4: Yeo and the developmental instability model of schizophrenia Flaw: While being a very intriguing theory, it lacks any empirical evidence at this point in time. It should be considered speculatively Flaw: While being a very intriguing theory, it lacks any empirical evidence at this point in time. It should be considered speculatively

11. Schizophrenia as an Evolutionary Advantage Schizophrenia paradox: “The discrepancy between high prevalence rate and reduced fecundity” Schizophrenia paradox: “The discrepancy between high prevalence rate and reduced fecundity” This doesn’t seem very adaptive, does it? This doesn’t seem very adaptive, does it? There must have been some evolutionary advantage to having schizophrenia… There must have been some evolutionary advantage to having schizophrenia…

12. Advantageous Theories Theory #1: Huxley, Mayr, Osmond, and Hoffer published the first model linking schizophrenia to evolutionary concepts. (1964) Speculated that reduced fecundity was compensated by higher resistance to allergens, shock, and infection Theory #1: Huxley, Mayr, Osmond, and Hoffer published the first model linking schizophrenia to evolutionary concepts. (1964) Speculated that reduced fecundity was compensated by higher resistance to allergens, shock, and infection Flaw: No substantial evidence supporting this theory Flaw: No substantial evidence supporting this theory

13. Advantageous, Cont. Theory #2: Kellet’s model suggesting that certain characteristics found in schizophrenia may have helped man’s territorial instincts Theory #2: Kellet’s model suggesting that certain characteristics found in schizophrenia may have helped man’s territorial instincts Flaw: This theory addresses only a small component of schizophrenia, providing no evolutionary explanation for psychotic symptoms Flaw: This theory addresses only a small component of schizophrenia, providing no evolutionary explanation for psychotic symptoms

14. Advantageous, Cont. Theory #3: The schizophrenia gene could possibly benefit individuals who carry it but do not have the disorder Theory #3: The schizophrenia gene could possibly benefit individuals who carry it but do not have the disorder Karlsson studied a population of schizophrenics in Iceland and discovered that first-degree relatives were twice as likely to be members of creative professions than the general population Karlsson studied a population of schizophrenics in Iceland and discovered that first-degree relatives were twice as likely to be members of creative professions than the general population Flaw: Providing an accurate association between psychiatric conditions and creativity can be difficult Flaw: Providing an accurate association between psychiatric conditions and creativity can be difficult

15. Conclusion Although there are many theories regarding the origins and possible evolutionary advantages/disadvantages of schizophrenia, none of them have truly been proven Although there are many theories regarding the origins and possible evolutionary advantages/disadvantages of schizophrenia, none of them have truly been proven Up until the 1960’s, studying schizophrenia from an evolutionary perspective was unheard of. However, this can only add to our understanding of this severe disorder and will hopefully one day benefit those who suffer from schizophrenia Up until the 1960’s, studying schizophrenia from an evolutionary perspective was unheard of. However, this can only add to our understanding of this severe disorder and will hopefully one day benefit those who suffer from schizophrenia

16. The End!