Biological Explanation of Unipolar Depression.

One biological explanation for unipolar depression is the monoamine hypothesis. The monoamines are a group of neurotransmitters which include serotonin, noradrenaline and dopamine. You will recognise the latter, dopamine, from the biological offering of an explanation for schizophrenia. The monoamines are believed to regulate mood. One of the functions of serotonin is to regulate the other neurotransmitters. Without the regulation provided by serotonin, erratic brain functioning and thinking patterns occur. Low levels of serotonin produces low levels of noradrenaline (a neurotransmitter needed for alertness, energy, anxiety and attention to life). Evidence suggests that low levels of noradrenaline cause depression, and high levels cause mania, which suggests it is involved both in unipolar and bipolar depression. Dopamine is also related to feelings of alertness, motivation and attention, and so it is suggested low levels of dopamine similarly are linked to depression. Essentially the monoamine hypothesis suggests that low levels of dopamine and low levels of noradrenaline result in depressive moods, and low levels of serotonin mean low levels of noradrenaline. It can therefore be low levels of dopamine or noradrenaline that result in depression, or a mixture of both. The hypothesis is used to work with drug treatment, so that the correct drugs (antidepressants) can be prescribed based on the particular monoamine in question. In other words, when a clinician is presented with a patient, they will choose the correct drug that alleviates the presented symptoms of depression. Most antidepressants work by increasing levels of serotonin.
It cannot be concluded that the explanation for depression is strictly biological. The diathesis-stress model explains how some mental disorders can have a biological underlying cause but require an environmental trigger to become active.
Evaluation:
One strength of the biological explanation of depression is that there is further