Evolutionary paradox of mental disorders

Question 1

Explanation 1: Direct vs. inclusive fitness

Answer 1

Reduced direct fitness - fertility rates of those with MDs.

Potentially enhanced inclusive fitness - increased fertility of relatives.

Question 2

Explanation 2: paternal age effect - mutation accumulation

Answer 2

Most MDs associated with a genetic component.

Accumulation of chance mutations - increased levels with fathers age (eg. schizophrenia).

Question 3

Explanation 3: early prenatal preparation and early plasticity - human brain development

Answer 3

High levels of plasticity before birth and during early stages (synaptogenesis and myelination) .
- more vulnerable to environmental effects.

Question 4

Explanation 3:… genes and environment

Answer 4

Stressors (eg. drugs, stress, infection etc) enhance risk of MDs.
- risk of CNS disorders increased: ASD (childhood), schizophrenia (adolescence), MDD (lifelong), diabetes/alzheimers (later life).

Question 5

Explanation 3:… prenatal preparation effects

Answer 5

Adaptive development plasticity and unanticipated environments.
- foetal development suggests a neonate is primed to expect a certain environment (inconsistent = illness).

Question 6

Explanation 3:… may be neurodevelopmental disorders

Answer 6

On a continuum (eg. ASD, ADHD etc).

- why is development often between childhood and adolescence?

Question 7

Explanation 3:… brain development in adolescents

Answer 7

Limbic system plays role in: emotions, motivation, emotional learning.

PFC in: working memory, planning, inhibiting inappropriate responses, risk taking etc.

PFC development believed to underlie age-related changes in: cognitive function, judgement, decision making.
- mismatch usually leads to stress - may be due to lacking development.

Question 8

Explanation 3:… why do changes happen so late?

Answer 8

Neurodevelopmental hypothesis: infant -> brain damage -> to DLPFC.

• age one year - little effect of lesion, performs almost as well as undamaged monkeys.
• 2 years - clear effect, performs worse.

Question 9

Explanation 3:… synaptic pruning in schizophrenia

Answer 9

Synaptic over-pruning hypothesis (Feinberg, 1982): too excessive neural pruning in PFC in post-natal development prior to onset of disorder .
- Glanz & Lewis (2000) - healthy adult = dendrites with many spines; schizophrenic adult = only a few spines.

Question 10

Explanation 3:… white matter reduction in schizophrenia

Answer 10

Loss of myelin sheath and reduced white matter in schizophrenic patients - eg. reduced corpus callosum volume.

Leads to disrupted disrupted communication with the brain -> loss of timing.

Question 11

Basic ideas of evolution of MDs

Answer 11

Continuum of mental illness.

Initially adaptive traits become maladaptive - adaption theories.

Mismatch between adaptive trait and current environment - mismatch theories.

MD as a by-product of an adaption - by-product theory.

MD due to random noise (mutations) - eg. paternal age effect.

THEORIES NOT EXCLUSIVE OF EACH OTHER.

Question 12

Evolutionary theory 1: The dopamine theory (An adaption theory) - human migration out of Africa

Answer 12

Enhanced brain size.

Homo-neatheralenis coexisted/interbred with homosapiens but died out 28000 years ago.

Migrated from Africa -> Europe -> Australia -> North America -> South America.
As human species evolved, brain enlarged (especially PFC).

Question 13

Evolutionary theory 1:… adaption of people

Answer 13

Migration (for resources) requires individuals to be adaptive, curious, risk taking etc.

• trade off - more likely to be killed.
• these traits vary in monkey species and humans (Fairbanks, 2001).

Dopamine levels linked.

Question 14

Evolutionary theory 1:… rise of dopamine levels in human evolution

Answer 14

Risk taking related to increased dopamine.

Goal directed behaviour/cognitive capacities related to increased dopamine, increased PFC.

Pathways:

• nigostriatal - motor action.
• mesolimbic - emotions, exploratory behaviour, motivational drive, creative impulse.
• mesocortical - reward-seeking behaviour, planning, problem solving etc.

Question 15

Evolutionary theory 1:… why did levels increasing during evolution?

Answer 15

Dopamine is important for attending to distant space and time (Pevic, 2009) - migration?

Near vs distant space - planning to reach something far away; imagination of more distant and abstract worlds.

Near vs distant time - planning behaviour (eg. food hoarding); distant goals (motivational behaviour); imagining the large time scale of evolution.

Adaptation to new environments due to:

• environmental pressures - increased consumption of meat and fish - greater supply of dopamine precursors - increased longevity in humans.
• population pressures.
• migration.
• stress levels - physiological responses to increasingly stressful and new environments.

Question 16

Evolutionary theory 1:… support

Answer 16

Dopamine level adaptation can be due to:
- genetic and epigenetic inheritance (eg. mothers can pass prenatal high dopamine levels to their offspring).

Dopamine levels across species (Previc, 1999; 2009).

• high dopamine - intelligent non-human species (eg. dolphins).
• very high - primates and humans.

Dopamine levels across societies (Previc, 2009; 1999) - modern industrial societies might have higher dopamine levels compared to agricultural societies.
- higher achievement motivation, increased competition.

Question 17

Evolutionary theory 1:… mental disorders and dopamine

Answer 17

Schizophrenia: clear relation between D2 receptor blocking and therapeutic effect.
- accounts for positive symptoms.

Other hyper DA disorders: autism, OCD, mania etc.

May be originally adaptive trait of mild dopamine levels, has become maladaptive.

Question 18

Evolutionary theory 2: by-product theory - mental illness = by-product

Answer 18

Eg. creativity: capacity to create new valuable ideas.
- Includes intrinsic motivation, expertise, intelligence, personality, psychopathology, etc.

Intelligence: humans - positively correlated between creative and IQ up to 120.

Thinking style: convergent and divergent thinking, use of analogies.
- chimp Sarah chose can opener instead of paint brush for closed paint can (Holyark & Thagard, 95).

Personality differences: Drives, Big5, capacities etc (Runco, 2007).
- some male vervet monkeys are bold and novelty seeking temperament (King et al, 1999).

Psychopathology: abnormal and maladaptive thought process; in mild form can contribute to creativity.
- eg. filtering out irrelevant info - increased odds of new ideas.

Question 19

Evolutionary theory 2:… creativity

Answer 19

Schizophrenia link (Previc, 2009; Carson et al, 203).

Reduced latent inhibition - reduced tendency to filter out irrelevant info.

Enhanced divergent and convergent thinking - lots of memory for ideas, observations, objects etc.

Loosened associations - more jumping from one topic to another.

• creativity - associations between remote ideas, well sorted and explained.
• psychosis - not organised, unusual, bizarre.

Question 20

Evolutionary theory 2:… creativity in high moods (bipolar disorder)

Answer 20

Hypomania - often part of bipolar disorders: manic/depressive.

• intense enthusiasm.
• overactivity.
• pressure to talk.
• flight of ideas etc.

Mania - often grandiosity and other traits take over and hospitalisation and medication is required.

Question 21

Evolutionary theory 2:… mental illness is a by product of creativity

Answer 21

Shared vulnerability model (Shelley & Carson, 2011):

• reduced latent inhibition - psychoactive drugs (Eg. LSD).
• novelty seeking - drugs and alcohol to stimulate creativity.
• hyper connectivity - synaesthesia.

Question 22

Evolutionary theory 3: Mismatch theory - mismatch theory

Answer 22

Adaptive trait in our ancestral environment becomes maladaptive in current environment.
- fears, phobias, depression etc.

Question 23

Evolutionary theory 3:… specific phobias

Answer 23

Ancient world - low fear threshold might have been advantageous.
- although includes false alarms, there is high cost of death/injury so beneficial to be wary.

Specific phobias - oversensitive fears(eg. spiders-hardly any harmful to humans).

• primary (inherent/unconditioned) - once posed a threat to ancestors maybe due to evolutionary stress.
• secondary (learned/modern) - eg. flying, dentists etc.

Question 24

Evolutionary theory 3:… depression

Answer 24

Associated with reduced serotonin levels.

Depression due to unfavourable changes:

• eg. loss of partner/child.
• one’s place in social hierarchy - vervet monkeys: changing serotonin levels with ranking (McGuire & Troisi, 1998) - humans: social place, pride and shame.

Hypothesis = depression and anxiety increased in modern society.

• because media bombards with info about those in better places than us?
• always hierarchy happening in bigger circle.
• social comparison theory (Festinger, 1954).