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Mental Illness
DSM IV (Diagnostic and Statistical Manual
of Mental Disorders, fourth edition.
This has no theoretical basis; that is, it is
based no theory about the cause(s) of
mental disorders.
Presently, its main function has to do with
insurance coverage.
Possible evolutionary causes of behavioral
disorders. Why above mutational
levels?
1. Not disorders, but defenses.
2. Side effects of genes with fitness
benefits.
3. Frequency dependent selection.
4. Missing or malfunctioning module.
5. Mismatch between present
environment and EEA.
6. Extremes of normal polygenic
distribution.
1. Not disorders, but defenses.
Analogy: fever.
Possible psychological example:
depression.
Withdraw from failing strategies.
Negotiate for more support.
2. Side effects of genes with fitness
benefits.
Analogy: sickle-cell anemia.
Possible psychological examples:
schizophrenia; bipolar disorder.
Both heritable.
Fitness benefits to (self or) other
carriers of the same gene.
2a. Bipolar disorder (manic depression;
severe mood swings).
May be very productive during manic
phases.
Relatives show high intelligence and
creativity.
2b. Schizophrenia; disintegration of self.
Hear voices, inappropriate emotion,
incoherent thoughts, experience “alien
control.”
Like Bipolar Disorder, relatives of
schizophrenics show high intelligence
and creativity.
Also may be example of defective
module (see below).
3. Frequency dependent selection.
Analogy: “transvestite behavior” in
hanging flies.
Possible psychological example:
sociopathy: Superficially charming and
sociable but egocentric, impulsive and
lacking in emotions of shame, guilt,
indebtedness.
Could exist at low frequency in a
population of reciprocal altruists.
3. Frequency dependent selection.
Analogy: “transvestite behavior” in
hanging flies.
Possible psychological example:
sociopathy: Superficially charming and
sociable but egocentric, impulsive and
lacking in emotions of shame, guilt,
indebtedness.
Could exist at low frequency in a
population of reciprocal altruists.
4. Missing or malfunctioning module.
Analogy: inability to feel pain.
Possible psychological example:
Autism: Impaired in social interaction,
poor eye contact, lack of emotional
tone, delayed and repetitive language,
preoccupation with objects, repetitive
behaviors.
Defective theory of mind module.
(Why? Modular view just identifies the
natural cleavage points.)
5. Mismatch between present
environment and EEA.
Analogy: dietary cravings that lead to
obseity.
Possible psychological example: Anxiety
disorders.
Novel dangers ->increased vigilance
Many strangers
Media amplification of risks
6. Extremes of normal polygenic
distribution.
Analogy: any polygenic trait.
Possible psychological example: Clinical
depression: Overly sensitive to
discouragement.