Depression, a debilitating illness characterised by a persistent depressed mood that impairs normal function, exerts an enormous health and financial cost worldwide. Diagnosis of depression is complex, as not all people experience the same symptoms, with diagnosis based on a series of questions as no biological test is currently available. This is due to the fact that the causes of depression have yet to be fully elucidated, although development of depression appears to be dependent on both genetic and environmental factors. While there is no cure for depression, psychological, pharmacological and brain stimulation approaches successfully manage the symptoms of many patients. However, there are patients that are refractive to current treatments, highlighting the need for improved diagnostics and therapeutics. For this, increased understanding of the neurobiology underlying depression is necessary, requiring further research utilising both animal models of depression and human clinical studies.

Key Concepts

  • The diagnosis of depression is complex, is based on the types and duration of the symptoms and is commonly complicated by the presence of comorbid conditions.
  • While there is no cure for depression, symptoms of depression can be managed through a variety of cognitive, pharmacological and brain stimulation approaches.
  • Depression is thought to result from a combination of genetic and environmental factors.
  • Human imaging studies suggest that depression is correlated with activity changes in multiple brain regions.
  • Animal models are necessary to investigate the neurobiological mechanisms that lead to depression and to test novel therapeutic strategies.

Keywords: stress; antidepressant; imaging; glucocorticoid; serotonin; norepinephrine; animal model

Figure 1. Typical monoamine antidepressants act by increasing neurotransmitter (green boxes, NE/5H‐T) in the synapse. Many achieve this by blocking the activity of presynaptic reuptake transporters (yellow, NET/SERT), which normally limit neurotransmission by taking the neurotransmitter back up into the presynaptic terminal (left panel). Blocking reuptake increases binding and activity of postsynaptic neurotransmitter receptors (blue, right panel).


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Kaska, Sophia, and Mazei‐Robison, Michelle(Mar 2016) Depression. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0025796]