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Schizophrenia as a Schizophrenia as a “Polythetic Construct”“Polythetic Construct”

• No single characteristic symptomNo single characteristic symptom

• Many symptoms, all present in Many symptoms, all present in some, not present in allsome, not present in all

• Manifestations in thinking, emotion, Manifestations in thinking, emotion, interpersonal relationshipsinterpersonal relationships

• A multisystem diseaseA multisystem disease

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What are the Characteristic What are the Characteristic Symptoms of Schizophrenia?Symptoms of Schizophrenia?• Depends upon whom you askDepends upon whom you ask

• Depends upon theoretical Depends upon theoretical constructconstruct

• Depends upon what you mean by Depends upon what you mean by characteristiccharacteristic

Common?Common?

Specific?Specific?

CoreCore?

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Kraepelin: The Borders Kraepelin: The Borders of Schizophreniaof Schizophrenia

……it is certainly possible that it is certainly possible that its borders are drawn at its borders are drawn at present in many directions present in many directions too narrow, in others perhaps too narrow, in others perhaps too wide.too wide.

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Boundaries of the ConceptBoundaries of the Concept

• Schizoaffective DisorderSchizoaffective Disorder

• Psychotic Mood DisordersPsychotic Mood Disorders

• Nonpsychotic disordersNonpsychotic disordersSchizotypal PersonalitySchizotypal Personality

Simple SchizophreniaSimple Schizophrenia

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““Good Prognosis Good Prognosis Schizophrenia”Schizophrenia”

• Prominent affective symptomsProminent affective symptoms

• Acute onsetAcute onset

• Family history of affective disorderFamily history of affective disorder

• Good premorbid function Good premorbid function

• Presence of insightPresence of insight

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Narrowing of Concept: Narrowing of Concept: RationaleRationale

• Risk of tardive dyskinesiaRisk of tardive dyskinesia• Risk of erroneously treating Risk of erroneously treating

mood disorders with mood disorders with neurolepticsneuroleptics

• Risk of self-fulfilling Risk of self-fulfilling prophesies of poor outcomeprophesies of poor outcome

• Risk of political abuseRisk of political abuse

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Single or Multiple Single or Multiple IllnessesIllnesses

• Whether dementia praecox in the Whether dementia praecox in the extent here delimited represents extent here delimited represents one uniform disease, cannot be one uniform disease, cannot be decided at present with certainty.decided at present with certainty.

-- Emil Kraepelin-- Emil Kraepelin

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Heterogeneity: Heterogeneity: Competing ModelsCompeting Models

• Single disease entity: multiple Single disease entity: multiple sclerosissclerosis

• Multiple disease entities: mental Multiple disease entities: mental retardationretardation

• Multiple domains of Multiple domains of psychopathologypsychopathology

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Single Disease EntitySingle Disease Entity

• A single illnessA single illness

• A single cause that produces A single cause that produces diverse manifestationsdiverse manifestations

• Possible mechanism: Possible mechanism: process producing multiple process producing multiple brain lesionsbrain lesions

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Multiple Disease EntitiesMultiple Disease Entities

• ““The group of schizophrenias”The group of schizophrenias”

• Multiple causesMultiple causesPurely genetic forms, e.g. phenylketonuriaPurely genetic forms, e.g. phenylketonuria

Purely environmental forms, e.g. virally inducedPurely environmental forms, e.g. virally induced

Multifactorial formsMultifactorial forms

• Manifestations reflect site of injury Manifestations reflect site of injury and time of the maturational and time of the maturational processprocess

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Multiple DomainsMultiple Domains• Multiple dimensions of Multiple dimensions of

psychopathology psychopathology e.g., psychotic, disorganized, negativee.g., psychotic, disorganized, negative

• Different mechanism for each dimensionDifferent mechanism for each dimension

• Disease process A Disease process A dimension A dimension A

• Disease process B Disease process B dimension B dimension B

• Disease process C Disease process C dimension C dimension C

• Mixed clinical presentation due to Mixed clinical presentation due to multiple disease processesmultiple disease processes