Biological explanations of depression

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Biological explanations of depression
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Research

• Family
• Twin
• And adoption studies
• These suggest the involvement of genetic factors

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Family studies

• Gershon reviewed a number of family studies
• He found that depression runs in families
• As the rate of depression was 2-3 times more in
  1st degree relatives of depressives
• Compared to the general population

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AMISH COMMUNITY

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Family studies continued...

• Egeland et al studied the Amish
• A small religious community in Pennsylvania
• Had a low incidence of major depressive illness
  compared to surrounding communities
• 1 family was studied which had an extremely high
  level of bipolar disorder
• 11 out of 81 members had manic depression
• Genes examined - 2 marker genes on chromosome 11
  were different
• These genes were neighbours of genes involved
  in the production of monoamines
• A biochemical implicated in depression

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Family studies evaluation

• Gene-mapping studies are very useful BUT
• No further research has supported Egelands
  findings
• Hodgkinson studied extended families in Iceland
• No evidence of the different genes in relation to
  manic depression
• Its possible that patterns of interactions in
  families may be the factor accounting for
  depressive illness

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Adoption studies

• Wender found that biological relatives of adopted
  sufferers from major depression
• were 8 times more likely than adoptive
  relatives to develop major depression

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Twin studies

• Allen reviewed relevant studies
• Mean concordance
• MZ 40 DZ 11
• Mean concordance for bipolar
• MZ 72 DZ 14
• Bertelsen, Harvald Hauge
• For major depression
• MZ 59 DZ 30
• For bipolar
• MZ 80 DZ 16
• In the population 5 diagnosed with major
  depression 1 with bipolar
• All figures for MZ DZ are much higher
  suggesting a genetic link

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Brain biochemistry

• Possibility that depressed patients have
  elevated/reduced levels of neurotransmitters
• Permissive amine theory
• Proposed that levels of noradrenaline dopamine
  are controlled by serotonin
• When serotonin is low - levels of noradrenaline
  fluctuate wildly
• Low levels depression, high levels mania
• Low levels of serotonin may be genetically
  inherited

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Mood monoamine transmitters

• Teuting, Rosen Hirschfield
• Compared substances in urine of depressed
  patients normals
• Compounds which are a by-product of the action of
  enzymes on noradrenaline serotonin
• Were present in small amounts in urine of
  depressed patients
• Suggests they have lower levels of these
  neurotransmitters
• Hard to tell if high or low levels caused
  depression
• Or whether depression caused the low levels of
  neurotransmitters

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Anti-depressants

• Increase levels of noradrenaline serotonin to
  reduce symptoms
• Drugs affect neurotransmitter levels rapidly BUT
  take longer to reduce symptoms
• These drugs do not provide direct evidence of
  what causes depression in the 1st place
• Macleod called this the TREATMENT AETIOLOGY
  FALLACY
• - The mistaken notion that the success of a
  treatment reveals the cause of the disorder

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Endocrine system

• Produces hormones that influence behaviours e.g.
  sleep, menstruation, growth
• Lots of conditions are linked to hormone changes
  where depression is a major symptom
• E.g. pre-menstrual syndrome
• Postpartum depression

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Pre-menstrual syndrome (PMS)

• Menstrual cycle involves changes in levels of
  oestrogen progesterone over a month
• Symptoms occur in the week or two before
  menstruation
• E.g. bloating, irritability, headaches
  depression
• These are due to hormone changes

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PMS research

• Abramamitz, Baker Fleischer
• Studied female admissions to a psychiatric
  hospital
• 41 entered the day before of the 1st day of
  their period
• Another study looked at normal women
• Found depressive symptoms intensified in 41 of
  women during the pre-menstrual period

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Postpartum depression (PPD)

• 20 of women report moderate depression after
  giving birth
• A few become chronically depressed
• Symptoms include sadness, tearfulness, anxiety
• Women go through massive hormonal changes after
  giving birth
• This is one possible explanation

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PPD continued ...

• Another possibility is that levels of the stress
  hormone cortisol are v.low after birth
• This may make it more difficult for women to cope
  with stress in the period after birth
• Most women who suffer from PPD have episodes of
  clinical depression
• Suggesting PPD is a combination of hormonal
  imbalances pre-existing predisposition to
  depression
• Lack of emotional support, low self-esteem, and
  unrealistic ideas about motherhood are also found
  in PPD
• Suggesting psychological factors are important