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Explanation 1: Direct vs. inclusive fitness

Reduced direct fitness - fertility rates of those with MDs.

Potentially enhanced inclusive fitness - increased fertility of relatives.


Explanation 2: paternal age effect - mutation accumulation

Most MDs associated with a genetic component.

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


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

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


Explanation 3:... genes and environment

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).


Explanation 3:... prenatal preparation effects

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


Explanation 3:... may be neurodevelopmental disorders

On a continuum (eg. ASD, ADHD etc).
- why is development often between childhood and adolescence?


Explanation 3:... brain development in adolescents

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.


Explanation 3:... why do changes happen so late?

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.


Explanation 3:... synaptic pruning in schizophrenia

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.


Explanation 3:... white matter reduction in schizophrenia

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.


Basic ideas of evolution of MDs

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.



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

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).


Evolutionary theory 1:... adaption of people

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.


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

Risk taking related to increased dopamine.

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

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


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

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.


Evolutionary theory 1:... support

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.


Evolutionary theory 1:... mental disorders and dopamine

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.


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

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.


Evolutionary theory 2:... creativity

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.


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

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.


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

Shared vulnerability model (Shelley & Carson, 2011):
- reduced latent inhibition - psychoactive drugs (Eg. LSD).
- novelty seeking - drugs and alcohol to stimulate creativity.
- hyper connectivity - synaesthesia.


Evolutionary theory 3: Mismatch theory - mismatch theory

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


Evolutionary theory 3:... specific phobias

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.


Evolutionary theory 3:... depression

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).