SCHIZOPHRENIA

1
SCHIZOPHRENIA

• Special Lecture
• Kevin Silber
• Staffordshire University

2
Lecture Overview

• In this lecture we will explore the following
• An overview of schizophrenia
• The positive and negative symptoms
• The heritability of schizophrenia
• The dopamine and glutamate hypotheses of
  schizophrenia
• Schizophrenia as a neurological disorder
• Evolutionary theories of schizophrenia
• Summary

3
Learning Outcomes

• By the end of this sessions you should
• Understand the symptoms associated with
  schizophrenia
• Appreciate that there are different theories that
  attempt to explain the origins of schizophrenia
• Recognise that schizophrenia might have survived
  as an adaptive trait

4
SCHIZOPHRENIA OVERVIEW

• It is the most common psychosis.
• Schizophrenia literally means split mind.
  However, this makes it the most misused
  psychological term as schizophrenia does not
  really manifest as a split or multiple
  personality.
• The term was invented by Eugen Bleuler to refer
  to patients who had a misplaced sense of reality.
• Schizophrenia occurs in approximately 1 of the
  worlds population.
• It is characterised by positive and negative
  symptoms which we now look at in more detail.

5
POSITIVE AND NEGATIVE SYMPTOMS

• A positive symptom is one that appears to reflect
  an excess or distortion of normal functions.
• A negative symptom is one that appears to reflect
  a diminution or loss of normal functions.

6
POSITIVE AND NEGATIVE SYMPTOMS

• Positive Symptoms
• These are symptoms that make themselves known by
  their presence.
• They generally include thought disorder,
  hallucinations and delusions. We will look at
  these in more detail shortly.

7
POSITIVE AND NEGATIVE SYMPTOMS

• Negative Symptoms
• These are symptoms which involve an absence of
  normal behaviour. They are not exclusive to
  schizophrenia.
• The symptoms include flattened emotional
  responses, decreased speech and social
  withdrawal.

8
POSITIVE SYMPTOMS OF SCHIZOPHRENIA

• Thought Disorder
• This involves irrational thinking. Schizophrenics
  cannot organise their thoughts well and often
  jump from topic to topic.
• Hallucinations
• The most common are auditory hallucinations.
  Typically, schizophrenics hear voices talking to
  them and these voices can tell them to do
  something or tell them that they are bad.

9
POSITIVE SYMPTOMS OF SCHIZOPHRENIA

• Delusions
• These are beliefs that are contrary to the truth.
  Typically, schizophrenics suffer delusions of
  persecution or delusions of grandeur.

10
HERITABILITY OF SCHIZOPHRENIA

• Schizophrenia appears to be heritable which is
  good evidence for it being a biological disorder.
  Both adoption studies (Kety et al., 1968) and
  twin studies (Gottesman and Shields, 1976) have
  supported a genetic link.
• However, it does not appear to be caused by a
  single gene as less than 50 of the children
  whose parents are both schizophrenic have the
  disorder.

11
HERITABILITY OF SCHIZOPHRENIA

• Thus, schizophrenia is either caused by several
  genes or the genetic involvement produces a
  propensity for the disorder.
• The latter suggestion has some supporting
  evidence (Gottesman and Bertelsen, 1989).

12
THE DOPAMINE HYPOTHESIS OF SCHIZOPHRENIA

• Dopamine is a neurotransmitter substance in the
  brain
• It plays a mediating role in reward and is
  involved in motor functioning
• However, it is probably its role in attending to
  salient events that is linked to schizophrenia

13
THE DOPAMINE HYPOTHESIS OF SCHIZOPHRENIA

• This is the favoured hypothesis of many working
  in this field.
• The hypothesis suggests that the cause of
  schizophrenia is an excess of dopamine which
  results from an over-activity in mesolimbic and
  mesocortical dopaminergic neurons.
• Even before the hypothesis was in place,
  psychiatrists were prescribing drugs, such as
  chlorpromazine, which had antipsychotic effects.

14
THE DOPAMINE HYPOTHESIS OF SCHIZOPHRENIA

• We now know that these drugs block dopamine
  receptors or, like apomorphine, facilitate such a
  block and so reduce the effect of the
  overproduction and over-release of dopamine.
• Conversely, drugs which increase dopamine
  activity, such as L Dopa, produce the positive
  symptoms of schizophrenia.
• One must be cautious about accepting the dopamine
  hypothesis too readily. There are two main
  problems.

15
THE DOPAMINE HYPOTHESIS OF SCHIZOPHRENIA

• Firstly, up to one-third of all schizophrenic
  patients are not aided by antipsychotic drugs.
• Secondly, one side effect of antipsychotic drugs
  is believed to be tardive dyskinesia. This is a
  problem for Parkinsons patients who are given
  too much L Dopa.
• If tardive dyskinesia is the result of too much
  dopamine then why should it result from
  antipsychotic drugs which are supposed to reduce
  the level of dopamine?

16
THE DOPAMINE HYPOTHESIS OF SCHIZOPHRENIA

• The answer might be a phenomenon called
  denervation supersensitivity
• This is when the receptors in the region where
  neurons have died become more sensitive to the
  smaller amounts of neurotransmitter substance
  around

17
THE GLUTAMATE HYPOTHESIS OF SCHIZOPHRENIA

• Another neurotransmitter substance called
  glutamate has been linked with schizophrenia
• Phencyclidine (PCP) is a potent psychotomimetic
• It produces phenomena akin to both the positive
  and negative symptoms of schizophrenia

18
THE GLUTAMATE HYPOTHESIS OF SCHIZOPHRENIA

• PCP blocks the receptors (NMDA receptors) that
  are usually activated by glutamate
• The suggestion is that schizophrenia might be the
  consequence of an under-activation of glutamate
  recptors
• Work is going on to develop drugs that might
  safely and specifically reactivate the affected
  receptor sites

19
SCHIZOPHRENIA AS A NEUROLOGICAL DISORDER

• Most schizophrenics show symptoms which would
  suggest that they are suffering from brain
  damage.
• Generally, evidence from CT scans suggests that
  there can be damage to the frontal lobes,
  temporal lobes and hypothalamus (Bogerts, 1989).
  Frontal lobe damage may account for some of the
  negative symptoms.
• Also, Andreasen (1988) has found evidence to
  suggest that the hippocampus and corpus callosum
  may develop abnormally in some schizophrenics.

20
(No Transcript)
21
SCHIZOPHRENIA AS A NEUROLOGICAL DISORDER

• The cause of such brain damage could be a viral
  disease although there is no direct evidence for
  this. Alternatively, it could be caused by
  obstetrical problems.

22
EVOLUTIONARY THEORIES OF SCHIZOPHRENIA

• Theories fall into two categories
• Schizophrenia as a disadvantageous by-product of
  human brain evolution
• Schizophrenia as an evolutionary advantage

23
EVOLUTIONARY THEORIES OF SCHIZOPHRENIA

• Evolutionary disadvantage
• Farley (1976) suggested it was an extreme variant
  of normal social behaviour
• Randall (1998) suggests it might be a consequence
  of abnormalities of functional connection in the
  brain
• Millar (1987) suggests it might be the result of
  a failure of integration between the limbic
  system and the cortex

24
EVOLUTIONARY THEORIES OF SCHIZOPHRENIA

• Crow (1995) believes there is a link between the
  evolution of schizophrenia and the evolution of
  language
• The two are tied by the lack of cerebral
  asymmetry and alterations in speech in
  schizophrenics
• Enhanced cerebral flexibility would boost
  intelligence and facilitate the emergence of
  language
• A by-product of flexibility would be a variation
  in psychological functioning resulting in
  psychosis

25
EVOLUTIONARY THEORIES OF SCHIZOPHRENIA

• Evolutionary Advantage
• Huxley, Mayr, Osmond and Hoffer (1964) reasoned
  that if schizophrenics were having fewer
  offspring because the disorder was
  disadvantageous, why was the prevalence rate of
  1 of the population being maintained?
• They reasoned that schizophrenia had advantageous
  and disadvantageous characteristics
• They speculated that the advantages might be
  resistance to allergy and infection but this has
  never been substantiated

26
EVOLUTIONARY THEORIES OF SCHIZOPHRENIA

• Stevens and Price (2000) have suggested a
  group-splitting hypothesis
• They suggest that tribal communities can only
  grow so big and then they must split so as to
  maintain optimal numbers
• The traits of schizophrenics might facilitate
  survival of the splinter group as they are often
  charismatic
• To support this they argue that these traits are
  found in charismatic leaders such as Hitler and
  Joan-of-Arc

27
EVOLUTIONARY THEORIES OF SCHIZOPHRENIA

• Polimeni and Reiss (2002) have suggested a
  variation on this theme
• They suggest that schizophrenia enhanced a
  shamans ability to conduct religious rituals
  within hunter-gatherer society
• Psychosis would be an advantage to the shaman and
  the prevalence of religious-based delusions in
  schizophrenia might support this argument

28
SUMMARY

• We have seen that schizophrenia has a number of
  distinctive features
• We have also seen that there are many theories as
  to the origins of schizophrenia
• These theories span biology and evolution and
  there are many more that have not been considered
  here
• No consensus yet exists and it is likely that
  there is more than one form of schizophrenia and
  more than one possible cause