The Medical Model

The medical model proposes that mental disorders can be understood in the same way as physical disorders i.e:

• biological causes underlie MI
• MI can be classified by looking at which symptoms occur together
• MI can be diagnosed by using a 'checklist' of symptoms
• biological treatments are appropriate for MI

The Biochemical Explanation of MI

• Brain cells transmit information in the form of electrical impulses around the brain
• Between brain cells are gaps (synapses)
• For info to pass from one cell to the next, neurotransmitters must pass across the synapse.
• Different neurotransmitters are important in different parts of the brain and are believed to be important in regulating different mental processes.
• One expl for MI is the possibility that symptoms are due to abnormal neurotransmitter levels or action.
• E.g. in Depression, if the level of a neurotransmitter (serotonin) is low then the message may not get across.

The monoamine hypothesis

This suggests that depression is due to abnormal levels of neurotransmitters in the monoamine group:

• noradrenaline
• serotonin
• dopamine

The role of serotonin includes the regulation of other neurotransmitters. If this doesnt occur, brain functioning can be erratic and faulty thinking patterns occur. Lack of serotonin appears to be associated with anxiety and compulsive behaviour and symptoms such as sleep disruptions. Low levels of serotonin can result in low levels of noradrenaline.

Noradrenaline needed to show alertness, energy, anxiety and attention to life, without it we see many symptoms of depression. Some anti-depressant drugs work by raising levels of noradrenaline. 

Dopamine is related to the ability to show reward and motivation, and to feel pleasure and reward. Low levels can lead to symptoms and so drugs can be given to raise levels of dopamine and alleviate symptoms.

This was expanded upon with the Permissive Amine Theory (Kety, 1975) which proposes that the level of noradrenaline and dopamine are controlled by serotonin, and that low levels of serotonin are inherited. When serotonin is low the levels of noradrenaline fluctuate widly; low levels are associated with depression and high levels with mania. The biochemical system depends in part on genetic factors and so the genetics and biochemical expls are inter-linked. (less reductionist than before)

Evidence Supporting:

• Antidepressant drugs such as MAOIs increase the levels of noradrenaline and serotonin and alleviate the symptoms of depression, similarly SSRIs inhibit the re-uptake of serotonin and the resulting increase in the level of serotonin is linked to improved mood.
• There are some drugs that decrease serotonin and these can cause depression
• Rampello, Noicoletti, and Nicoletti (2000) found that patients with major depressive disorder had an imbalance in several neurotransmitters, including noradrenaline, serotonin, dopamine, and acetylcholine.

Evidence challenging:

• Antidepressant drugs do not work for all patients. Also, the drugs increase the levels of the biochemicals immediately but can take weeks before they alleviate the depression.
• Correlational research cannot establish cause and effect. It is difficult to establish whether the low levels of neurotransmitters cause depression, are an effect of having the disorder, or are merely associated. Causation cannot be…