Biological explanation of depression

Biological explanations of dysfunctional behaviour centres around physiology, and refers to aspects of biology such as genetics and brain functioning. 

The biological explanation of depression specifically refers to two factors: neurotransmitter dysfunction and inherited genes. In terms of neurotransmitter dysfunction, the biological approach would explain that depression is significantly associated with low levels of serotonin, which has been also been associated with many forms of dysfunctional behaviour including excess anger, anxiety, poor social functioning and other mood disorders. Serotonin is believed to have a variety of roles, and affects brain functioning; though it is not known whether depression is caused by serotonin levels, or whether depression causes low serotonin, or if there is another factor causing them both.

In terms of genes, family research - especially twin and adoption studies - has shown there to be a genetic link to depression, and that this suggests some people may carry genes that predispose them to depression and other mood disorders. Thus, depression could be explained in terms of genetic predispositions.

One study which conducted family correlational research into depression was Wender et al. It was an adoption study which looked at whether environment or genetics appeared to be more associated with depression in adopted adults. The study used a sample of 71 adults who had been adopted and who had a mood disorder, and 71 controls with the same mean age who'd also been adopted but did not have a mood disorder. All had been removed from their mothers at a young age. Psychiatric evaluations were conducted of both the biological and adoptive parents to see whether there was a stronger correlation between depression in adopted adults and depression in adopted parents or biological parents. The results showed that there was an eight fold increase in unipolar depression among the biological parents of the adults. In other words, adoptive parents were eight times less likely to have depression, and the biological parents having depression correlated more significantly with depression in the adopted children than the adopted parents having depression. 

Thus mood disorders appear to have a genetic link, and biological psychologists would thus attribute depression to genetics.