Aetiologies of Unipolar Depression
Depression can be defined as ‘A condition of general emotional dejection and withdrawal; sadness greater and more prolonged than that warranted by any objective reason.’
The psychological pain depression brings is severe, long lasting and debilitating. It may intensify as the months go by. People with clinical depression may become unable to carry out the simplest of life’s activities, and some even try to end their lives.

Biological theory researchers have relied on genetic studies and on investigations into biochemistry to help explain the causes of unipolar depression.
Many theorists believe that some people inherit a predisposition to unipolar depression. Support comes from many sources – family studies, twin studies and adoption studies. Family studies select people with depression and examine their close relatives to see whether depression affects other members of the family. If a predisposition to unipolar depression is inherited then relatives should have a higher rate of depression than the general population. Research has supported this claim.
If the predisposition is inherited it would also be expected that more cases of depression would be apparent in close relatives compared to distant relatives. Twin studies are used as identical twins share 100% of the same genes, therefore if one twin has the disorder the other should also. Twin studies have found rates consistent with this expectation.

Evaluation which supports genetic theory of unipolar depression includes from Harrington et al, who found a 20% likelihood of developing depression in those with a relative with depression, compared to 10% of those with no depressive relatives.
This shows that it is twice as likely to develop depression if the individual has a close relative who has or has had the disorder, suggesting a genetic link.

Similarly, support comes from Gerschon (90), who reviewed 10 family studies of depression and found that between first-degree relatives, the chance of getting depression was between 7% and 30% - this is much higher than the general population and therefore suggests genetic factors are key in explaining the causes of depression.

However, criticism of this theory includes that although research has shown the risk for depression is higher for MZ twins, it is below 50%. Therefore this criticises the theory as it shows genetics is not the only factor in explaining depression.

Similarly in criticism, close relatives share similar environments, therefore it may be something in the environment causing depression, not the genetic fault.

Research has suggested that chemical imbalances could lead to depression. As certain chemicals are linked to mood, then an imbalance in these chemicals could cause a person’s mood to fluctuate or change.
Neurotransmitters are brain chemicals that carry messages from one nerve cell, or neuron to another. Norepinephrine ( Noradrenaline ) and Serotonin are the two neurotransmitters where reduced activity has been most strongly linked to unipolar depression (Zaleman 1995).
In the 1950’s several pieces of evidence pointed to the low activity of both Norepinephrine and Serotonin in causing depression.
Also, two groups of effective antidepressant medications – monoamine oxidase inhibitors (MAO) and tricyclics – were accidentally discovered. Both these types of drugs increase levels of either norepinephrine or serotonin activity in the brain.

Evaluation which supports biochemical theory of unipolar depression includes
Kety (75) – who suggests that depression is caused by a deficiency in noradrenaline. Noradrenaline is controlled by serotonin and dopamine, and when levels of the other two are low, noradrenaline levels may fluctuate.
This shows that low levels of certain neurotransmitters are closely linked to those who suffer from unipolar depression.

Similarly, support comes from Bunney & Davis 1965, Golden & Gilmore 1990, who stated that some theorists concluded that these neurotransmitters were perhaps to blame for the cause of unipolar depression. Investigators further concluded that the lower activity of these neurotransmitters must reduce neuron firing, which explains the slow movements of depressed people.
Therefore this again supports biochemical theory, as it gives a biochemical explanation for some of the key symptoms of depression, such as poor concentration/memory and general lethargy.
However, criticism of this theory includes that cause and effect cannot be established, as it may be that depression causes low levels of noradrenaline / serotonin, or that low levels of noradrenaline / serotonin cause depression. Therefore this criticises the theory as it is not clear cut that low levels of neurotransmitter is directly causing depression.
Furthermore, in criticism of the theory, more recent theories have suggested that another neurotransmitter – dopamine – may also play a part in unipolar depression, therefore suggesting more research is needed before conclusions can be made on which neurotransmitters play the biggest part in the causes of unipolar depression.

Alternatively, the behaviourist theory of Learned Helplessness states depression is learnt when individuals try but fail to control unpleasant experiences in their lives. Based on classical conditioning, individuals learn to associate unpleasant experiences with a lack of control. This then impairs their ability in tasks/situations that they can control.
An example of this could be long term unemployment, where an individual may associate constant rejection from job applications with a lack of control over employment prospects.
Evaluation which supports learned helplessness theory of unipolar depression includes Seligman & Maier (1967) – They placed dogs in boxes where they couldn’t escape from electric shocks, when placed in boxes where they could, they failed to try.
This study suggests that depression develops due to associating the unpleasant experience of electric shocks with a lack of control, which then causes general depressive symptoms, supporting Learned Helplessness theory.

Later studies on humans have supported the theory. Hiroto (1974) found college students who were exposed to uncontrollable unpleasant events while trying to solve puzzles, i.e. a loud irritating noise that they couldn’t turn off, were likely to fail on further cognitive tasks where the noise could be controlled.
This study suggests that individuals associate the unpleasant experience of loud noise with a lack of control, which then causes them to ‘give up’. This negative attitude can lead to general depressive symptoms, supporting Learned Helplessness theory.

However a problem with this theory is it’s based on animal research & animals & humans have very different cognitive processes, so therefore we can’t assume the theory will apply to humans.

The Interpersonal theory states that depression is caused by not having enough support from social networks, which makes difficulties and problems that may arise in daily life much more difficult to cope with. The behaviour of depressed people often makes this worse due a lack of social skills which can lead to rejection from others.

Evaluation which supports Interpersonal theory of unipolar depression comes from Black (1983) – who found that depressed outpatients who had higher social support networks had better scores on depression rating scale than those with poor social support

Similarly, support comes from research by Davila et al (1995), who found that poor interpersonal skills have been found to predict increases in depression among adolescents.

However criticism includes that there are cause & effect problems – it is hard to know whether depression is caused by lack of social support or whether depression causes social support to fall away.

To conclude, it is difficult to say whether depression is born or made as there are both supportive and contradictory arguments for all explanations. It may be that an individual is born biologically predisposed to depression, but will only later develop depression if this is triggered by, for example, having poor interpersonal skills or encountering stressful events and having little or no control over them. Therefore it is not possible to say whether depression is born or made, it depends on a combination of factors