MOOD DISORDERS - NEUROCHEMICAL and BRAIN STRUCTURE and FUNCTION EXPLANATIONS

neurochemical and brain structure and function explanations for mood disorders

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Neurochemical and brain structure/function explanations for mood
disorders
Neurochemical explanation
The limbic system plays a significant role in emotion and is linked to other areas of the brain,
such as the endocrine system and autonomic system, via neurotransmitter pathways
When neurotransmitters are in the synaptic cleft ­ only active for a short period of time ­ and
are then destroyed, inactivated or reabsorbed by cell ­ known as reuptake
Antidepressants e.g. imipramine block the synaptic reuptake, increasing their availability
Based on the effects and results of these drugs, it has been claimed that depression is due to
an insufficiency of neurotransmitters
However, mania results from an increased amount of neurotransmitters
Research to support this explanation:
Shastry (2005)
Evaluation of the neurochemical explanation
Difficulties began to emerge with this theory in a number of areas
Antidepressant medications were discovered that did not have the same effects as
mentioned, for example they increased the availability of neurotransmitters
Antidepressants immediately increase levels of neurotransmitters but there is a delayed
effect alleviating the symptoms ­ i.e. it can take several weeks for depression to begin to lift
The latest evidence that a simple increase in neurotransmitter levels do not explain why the
antidepressant drugs alleviate depression ­ they now believe that an interaction between
various neurotransmitters occurs
Brain structure and function explanation
There is some evidence that the limbic system and the frontal lobes are implicated in
depression
Injury or stroke that affects the frontal part of the brain can lead to depression ­ the frontal
lobes are a major regularity component of the limbic system and this system controls
emotion and drives
Neuroimaging studies have found structural abnormalities in the frontal region of the brains
of unipolar patients
Brain scans using techniques such as PET have identified four areas of the brain that show
abnormalities associated with depression, which are; prefrontal cortex, hippocampus,

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Each of these areas shows a common symptom of
depression, such as memory, mood, body's response to stress and goal related behaviour
Research to support this explanation:
Henrique and Davidson (1990) ­ discovered frontal hypoactivation in a sample of 15 unipolar
depressed patients, and was not found in normal controls
Coffey (1993) ­ using MRI demonstrated that depressed patients had a lower frontal lobe
volume than controls did
Evaluation
Findings that show deficits in the brain structures of depressed patients fail to unravel cause
and…read more

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