There are many different explanations for depression, including biological. Links have been found between biochemical, genetics and hormonal imbalances with depressed people.
In the biochemical explanation, a link has been found between neurotransmitter imbalances and depression. Serotonin is associated with pleasure and mood. Mann et al found impaired transmission of serotonin in people with depression.
However Julian disagrees with this statement and says depression may be due to neuron damage rather than a neurotransmitter reduction. The problem with this approach is that it implies correlation and not causation, there may be a link but something else could be causing both depression and low serotonin. There is the chicken and egg problem – does low serotonin cause depression or does depression cause low serotonin?
In other areas of psychology low serotonin has been linked with increased aggression and eating disorders, as well as anxiety. Someone that has low serotonin does not necessarily become depressed. There is also the problem where people are depressed but have normal serotonin levels. This shows that depression is not fully down to biochemical imbalances but other things as well. It is a very simplistic and reductionist model and should only be included as a vulnerability and not the whole answer to depression.
Another explanation is a genetic problem. Through many family studies Gershon states there is a clear inheritable component to depression, especially in bipolar disorder. Weisseman et al supports this by saying that for if a child has a parent with depression, the risk of the child having depression is increased by three times compared to the general population. This is a strong finding but as the children share the same environment as their parents, there is a possibility that the child has learnt the behaviour through the social learning theory of imitating and observing and