Etiology of Depression - Biology

Genetics Genetic factors may predispose people to depression

Nurnberger + Gershon (1982) reviewed twin study results found the higher concordance rate between MZ twins than for DZ twins

However this only means they are more likely to develop depression compared to people in the same circumstances without genetic predisposition

Correlation does equal causation

Caspi et al (2003) said that the results indicated that genetic factors moderate responses to environmental factors, and they also warm that speculations about clinical implications of these findings is premature

Neurotransmission depression may be caused by a deficiency in neurobiological

systems such as neurotransmitters and hormones

catecholamine hypothesis (Joseph Schildkraut 1965) suggest depression is associated with low levels of noradrenaline

theory was developed into the “serotonin hypothesis”, the idea that serotonin is the neurotransmitter responsible

Janowsky et al (1972) results showed that a depressed mood could be artificially induced by certain drugs

Delgado + Moreno (2000) found patients with MDD had an imbalance of several neurotransmitters, including noradrenalin, serotonin, dopamine, and acetylcholine

Neurotransmission cont.However this could indicate that having

depression caused these imbalances not vice versa – Burns (2003) says that he has never seen any convincing evidence that depression results from a deficiency of brain serotonin

Lacasse + Leo (2005) argue that contemporary neuroscience has failed to provide evidence that depression is cause by simple neurotransmitter deficiency. According to them, modern neuroscience has instead demonstrated that the brain is very complex and poorly understood

Hormones cortisol hypothesis says that stress can predispose an

individual to psychological as well as physical disorders

cortisol is a major hormone of the stress system

possible like between long-term stress and depression indicated by the fact that patients with MDD have high levels of cortisol

supported by findings from studies on victims of childe abuse

however the relationship between stress and depression is not yet well understood

people develop depression without previously being stressed, and people who have experienced terrible stress do not necessarily develop depression