Causes of Unipolar Depression

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  • Created by: VHNLN
  • Created on: 07-04-16 11:58

Unipolar Depression

Biological Approach: Monoamine Hypothesis

There are 3 different types of neurtransmitters : dopamine, serotonin and norepinephrine

It is thought that a lack of serotonin is a biological cause of unipolar depression. It could be down to genetic or environmental factors- the Diathesis-Stress model incorporates these theories. Unipolar depression could be triggered by stressors (stressful life events.) If a person has pre-existing genetic or environmental vulnerabilioty to depression.

The heritability of unipolar depression is 40% in women and 30% in men. This means that there is a genetic link. One study found that the serotonin transporter gene had a moderating effect on depression after a stressful life event. It seems that biological make up can pedispose one person to develop depression where another person in the same situation will not.



  • if the explanation is that there are monoamine deficiencies, and drugs that replace those deficiencies work, then this is evidence for the hypothesis.
  • The different monoamines link to different symptoms, treatment reflects those differences, supporting the hypothesis.


  • There are drugs (e.g. opipramol ) that affect depression but are not related to monoamines.
  • When monoamines are depleted in experiments, they do not cause symptoms of depression.
  • NRI scans have shown that there are physical differences in the brains of depressed people - this may be the caise reather than neurotransmitter functioning.
    • e.g a smaller hippocampus - drugs increasing serotonin levels may increase the hippocampal area. This may lift mood and improve memory, so serotonin may be a factor affecting brain mass and not monoamine deficiency (as the cause of the depression.)
  • A different biological explanation implicates arts of the nervous system related to stress and includes and increase int the levels of cortisol.

Cognitive Approach : The Cognitive Model of Depression

This model hypothesises that making changes to thinking patterns can affect the cause of the disorder - fulty thinking may be a part of the cause of such depression.


Table 1 (

Beck's Cognitive Model of depression includes faulty thinking- featuring negative and unrealistic ideas (see Examples...) that means…


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