Our current knowledge of depressive disorders

23rd Oct 2018

As the most occurring mental health problem in the world (1) and affecting more than 3% of people in England (2), depression is a debilitating mental condition characterised by anhedonia, irritability, sadness and other symptoms such as abnormal sleep and eating behaviour. 

This recent article by Kaltenboeck and Harmer (2018) in the BNA’s journal ‘Brain and Neuroscience Advances’ summarizes our knowledge of depressive disorders so far and describes what future research could focus on.  

The article starts by discussing current explanations for the disorders. For example, the neurochemical perspective describes how levels of certain neurotransmitters (dopamine, serotonin, noradrenaline and recently discovered also GABA and glutamate) are different in people with depression. It is these neurotransmitter levels that are changed with common antidepressants, which is how these drugs are thought to alleviate the symptoms. 

Moreover, the second explanation given is at the neuroendocrine level, where slight increases in cortisol, a hormone involved in stress, have been found in patients with depression and those at risk. 

The anatomical level describes abnormalities in the size and blood flow of the hippocampus (memory), several areas in the frontal lobe associated with planning, personality, decision-making and empathy (prefrontal cortex, orbitofrontal cortex and anterior cingulate cortex) and the basal ganglia (has various functions, such as emotion, movement, cognition and learning). 

And finally, the article mentions the cognitive explanation for depressive disorders, focussing on problems with attention, memory, executive function (e.g. decision-making) and issues related to processing information, since information and situations are more likely to be regarded as negative by people with depression. 

The future of depressive disorders research could concentrate on creating one explanation out of the previously mentioned explanations. Additionally, it may be useful to explore factors in the rest of the body, as for example a link between the brain and bacteria in the gut has been found. Lastly the article highlights the need to use the knowledge found in research to help patients more, as this is still fairly limited nowadays. 

For the full review article, click here

Kaltenboeck, A. and Harmer, C., 2018. The neuroscience of depressive disorders: A brief review of the past and some considerations about the future. Brain and Neuroscience Advances, 2, p.2398212818799269.

(1) Vos, T., Barber, RM., Bell, B., Bertozzi-Villa, A., Biruyukov, S., Bollinger, I., ...Murray, CJ.. (2013). Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: A systematic analysis for the Global Burden of Disease study. The Lancet, 386(9995), 743-800. 

(2) McManus S, Bebbington P, Jenkins R, Brugha T. (eds.) (2016). Mental health and wellbeing in England: Adult psychiatric morbidity survey 2014. Leeds: NHS digital.