Evolutionary Explanations of Mental Disorders

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Evolutionary Explanations of Mental Disorders

• Choose a topic for presentation
• Green Red
• Genome lag Increased fitness P219-220 P575-576
  
• Schizophrenia Depression P221-222 P577-578
• Anxiety Disorders including P222-224 P578-580
• phobias and OCD
• Evaluation P224 plus P580
• handouts

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Basic argument

• Mental disorders are not a recent
  development.Some mental disorders are
  inherited.The fact that these genes exist in the
  gene pool suggests they have adaptive
  value.However, people with these disorders are
  likely to have lower reproductive success.
  So Why
  havent the genes disappeared from the gene pool?

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GENOME LAG (p219)

• Most of our inherited behaviours evolved during
  the
• ENVIRONMENT OF EVOLUTIONARY ADAPTATION
• i.e. between
• 35,000 and 3 million years ago
• Some of these behaviours are not adaptive today,
  but have
• not been eliminated by natural selection.
• Genome lag refers to this lagging behind
  environmental
• changes.

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THE STRESS RESPONSE

• Fight or Flight adrenalin rush was important
  to survival in our evolutionary past.
• Those individuals with a rapid and effective
  response were more likely to escape from
  predators and survive.
• BUT
• This response mechanism is not suited to own
  present lifestyle.

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MODERN DAY STRESSORS

• Noise
• Overcrowding
• Pressure of Work
• Arguments
• It is better to respond to these by relaxation
• (parasympathetic branch of ANS)
• BUT
• It is the Sympathetic branch which is activated!
• (increased heart rate, blood flow, metabolic rate)

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STRESS AND MENTAL DISORDER

• So in the modern world, the stress response
• is not adaptive
• Running away is not desirable
• Modern stress situation tend to be ongoing so we
  would end up in Selyes 3rd Stage. What is it?

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FIGHT OR FLIGHT TODAY

• In our evolutionary history, automatic
  arousal would lead to safety (killing threat or
  running away from it) So then autonomic activity
  could return to normal.
• Today stressors do not go away and illness is
  the result.
• Mental illness may occur because we are not
  adapted to urban life.

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EVALUATION OF EVOLUTIONARY DETERMINANTS OF MENTAL
DISORDER (p219)

• 1 It could be argued that todays environment is
  not that different from our evolutionary past. We
  are still pre-occupied with
• Finding resources
• Forming relationships
• Raising children
• Coping with death, illness and injury

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AUTISM

• Autism is a mental disorder in children who
  cannot relate to others. (see film Rainman or
  book A curious incident of a dog in the night
• Yet autistic individuals sometimes have
• super-human abilities.
• This is also true for
• Van Gogh (painter) - Manic depressive
• John Stuart Hill (philosopher) - Autistic
• Leonardo da Vinci (painter) - Obsessive
• 3 This possibility leads to the notion of
  increased fitness

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INCREASED FITNESS (p219)

• Maybe genes for mental disorders are also
  responsible for other desirable traits eg.
  Schizophrenics sometimes believe they are Jesus
  Christ, or somebody powerful.
• This could be a desirable characteristic in good
  leaders, but taken to an extreme.

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PHYSICAL ILLNESS

• The body has evolved ways of protecting itself
  eg. vomiting when poisoned, coughing to remove
  viruses.
• Lizards when ill lie in the sun. This heats them
  up and kills pathogens which make them ill

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MENTAL ILLNESS

• Possibly these are adaptive too.
• Eg. Anxiety may be adaptive because it will lead
  an organism to avoid dangerous situations.
• So these genes could lead to
• INCREASED FITNESS
• Read Blue box p220 Sickle Cell Anaemia

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HUNTINGDONS CHOREA

• This disorder persists because it develops in
  adulthood, after breeding. Onset occurs in 30
  year olds
• Recessive genes (eg. Haemophilia, H.C) may
  remain in the gene pool because most of the time
  they are silent. They only manifest themselves
  when both parents carry the recessive gene they
  both get passed to the offspring.
• So there is little opportunity for the gene to
  be selected out of the gene pool.

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LOSS AND DEPRESSION

• Eg 2. A loser in a contest was more likely to
  survive if he accepts the loss because this
  will prevent further injury. This strategy is
  likely to involve becoming depressed.
• Eg 3. Nesse Williams account for increased
  depression in urban society by the genome lag.
  Urban life presents images of ideal lives and
  feeds into our ancestral competitiveness. This
  could produce dissatisfaction and longing which
  leads to depression.

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BIPOLAR DEPRESSION(MANIC DEPRESSION)

• Twin and adoption studies provide evidence for a
  strong genetic ling for manic-depression.
• The manic phase is thought to be related to
  creativity and charismatic leadership.
• This would be adaptive
• Eg. Winston Churchill
• Vincent Van Gough
• Abraham Lincoln
• Beethoven
• Graham Green
• All suffered from manic depression. Also, many
  famous people have a relative who suffers from it.

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ANXIETY DISORDERS

• People who suffer inappropriate amounts of fear
• Anxiety is
• 1) An emotion
• 2) Adaptive
• Anxiety places an animal in a state of arousal
  to deal with an environmental threat.
• It also ensures that danger is dealt with
  cautiously.
• Phobias and OCD are examples of disproportionate
  levels of anxiety. Natural anxiety levels have
  become exaggerated, possibly through classical
  conditioning.
• TASK Read and make notes on case study of
  Little Albert. Blue box p223 green.

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PHOBIAS

• A strong and irrational fear of something.
• Seligman PREPAREDNESS
• Some members of a species are more easily
  conditioned than others. This conditioning
  probably led people to safety in our ancestral
  past eg. Avoidance of snakes, heights and insects.

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THE FEAR RESPONSE

• Bennet-Levy and Marteau 84
• Correlational study Participants were given a
  list of 29 animals and asked to rank them on
• Perceived ugliness
• Perceived harmfulness
• Own fear of animal
• Fear strongly correlated with ugliness. Suggests
  an innate fear which leads to avoidance of the
  animal. This is also rewarding because it reduces
  anxiety levels.
• So a phobia could develop though
• First Classical conditioning (pairing)
• Second Operant conditioning (reward)

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Obsessive Compulsive Disorder

• Obsessive thoughts, compulsive acts.
• Compulsive rituals are often to do with hygiene
  eg. Washing or cleaning.
• The hygiene ritual lowers anxiety, and so is
  repeated.
• OCD has been shown to have genetic links. There
  would have been an evolutionary advantage to
  cleaning and hoarding.

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Evaluation of Mental Disorders Argument (p224)

• 1) This is a new way of looking for
  explanations of mental disorders and needs
  refining.
• 2) Evolutionary explanations assume behaviour
  is inherited. So it can explain why mental
  disorder tends to run in families.
• 3) It is a retrospective explanation, ie. We can
  only guess the reasons for maladaphive
  behaviours existing. So it cannot be proven.

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• 4) Evolutionary Psychiatry does not work in
  the same way as evolutionary medicine
• Cough Function of cough Root of problem
• Mental Neural mechanisms Describe the
  disorder
• Disorder involved
• However, attempting to understand why the
  behaviour may once have had an adaptive value,
  could lead to a better form of treatment