Download Biological Approach

Assumptions about causes:
Same as physical illness
 Brain
anatomy
 Infection
 Neurotransmitters/Chemical
imbalance
 Genetics
Chemical imbalance
Levels of chemicals in brain too high or
too low
 These chemicals transmit signals
between nerves
 Chemicals called neurotransmitters

psychlotron.org.uk
Vesicles release neurotransmitter
into synaptic cleft
psychlotron.org.uk
Neurotransmitter binds to
receptors & activates them
psychlotron.org.uk
Enzymes are released to break
down the neurotransmitter
psychlotron.org.uk
Excess neurotransmitter is taken
up by the pre-synaptic neuron
psychlotron.org.uk
Vesicles are replenished with new
& reused neurotransmitter
Chemical imbalance
Levels of neurotransmitters may be too high
or too low
 Depression- too low serotonin
 Schizophrenia – too high dopamine

Infection
Bacteria and viruses may lead to mental
disorders
 streptococcus infection has been
linked to OCD in some children

 glandular fever linked to anorexia
(only 4 patients)
 Today Show Saving Sammy PANDAS YouTube

Neuroanatomy
Damage to brain structures
 May be abnormal from birth or due to injury
 E.g. hypothalamus role in eating disorders
 Ventricles and schizophenia
Evidence:
 In mice if hypothalamus cut they either
starve or overeat

Mouse lesion hypothalamus
Schizophrenic twins
Genes

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inherit a tendency for mental disorders in
DNA from parents
Tested using:
Family studies e.g. schizophrenia 18x more
likely if 1st degree relative with it
Twin studies e.g. Comparing MZ (identical)
& DZ twins
Concordance rates (both have disorder)
Anorexia MZ 56%, DZ 7%
Bipolar disorder MZ= 80%, DZ= 16%
Gene Found At The Root of Hair-Pulling
Disorder - YouTube