Biological Level of Analysis In Depression

Serotonin Hypothesis

Catecholamine Hypothesis Suggested by Joseph Schildkraut in 1965 Depression is associated with low levels of noradrenaline Serotonin Hypothesis – depression

Janowsky et al. (1972) Participants given drug called ‘physostigmine’ Within minutes, profoundly depressed, self- hate, and suicidal wishes Mood change artificially, disturbance in neurotransmission? Drugs increasing noradrenaline reduce depression symptoms

Arguments Delgano and Moreno (2000) – depression may influence the production of neurotransmitters Rampello et al. (2000) – MDD patients imbalance of noradrenaline, serotonin, dopamine, acetylcholine – contradicted by Burns (2003) Lacasse and Leo (2005) – the brain is too complex to consider only one reason behind depression

So far.. Only one of the theories Research is less on the neurotransmitter, more on the process as a whole

Cortisol Hypothesis

Cortisol: hormone responsible for the stress system Belongs to stress hormones called glucocorticoids (plays role in fear and anxiety reactions) Patients with MDP have high levels of cortisol, indicating possible link

Over-secretion of cortisol may be linked to other neurotransmitters High levels of cortisol may: lower serotonin receptors Lowers dopamine levels Weaken the function of receptors for noradrenaline

Relationship between stress and depression It cannot be concluded that there is a causational or correlational relationship However high levels of cortisol are associated with depressive symptoms Drugs that normalizes cortisol levels help decrease depression symptoms

Effects of Depression Long term depression may lead to structural changes Decrease of glucorticoid receptors in the hippocampus and prefrontal cortex of suicidal victims Cushing’s syndrome results in excessive production of cortisol

Genetics Genetic predisposition/ vulnerability may explain depression Nurnberger and Gershon (1982): 7 twin studies Average concordance rate for MZ twins: 65% DZ twins: 14%

Duenwald (2003): 5-HTT gene: serotonin pathways responsible for controlling mood, emotions, aggression, sleep and anxiety Caspi et al (2003): Correlation between gene and depression does not indicate causation Genetic factors moderate responses to environmental factors