The musings of a fourth year English medical student

Thursday, 19 November 2015

WHAT IS DEPRESSION?

This may seem like a silly blog title. For many, depression is simply feeling low and being lazy. But today I decided that I wanted to discuss depression in more detail.

I think it's fair to say that in my friendship groups my friends are normally very comfortable confiding to me very personal information. My friends mean a lot to me and I always want to help. However, I have noticed that a lot of them find mental health diseases very bewildering. They always want to know what to say and what not to say to a sufferer of depression. How is depression something different to just having a bad day? 

To add more complexity to the disease of depression, each patient has unique symptoms. A common trend of symptoms will indicate depression, but not every symptom will be present in diagnosis. 




For me, depression is like a numbing agent to the brain. Activities I loved to do don't appeal anymore. A fantastic firework display is boring. Going out, having a nice meal; they don't feel exciting anymore. In addition, there is guilt and intense fear attached to everyday tasks and anything I do. I do not sleep well at all and often have back pain. 

One thing that should always be respected is that depression is a real disease and in fact a physical one. Whilst the brain is an incredibly complex and misunderstood organ, there are some things we  do know about it. We know that the neurotransmitter serotonin is used at the synapses of neurons that innervate the suprachiasmic nucleus. This is where most mammals regulate their body clocks. Any abnormalities in this otherwise normal process can lead to insomnia and fatigue. So, when a depressed person complains of those symptoms, there is reputable physiology behind them.  

Serotonin is believed to be play a role in other pathways, too. A new type of anti-depressants came out in the last 20 years called Selective-Serotonin-Reuptake-Inhibitors (SSRIs), the most common brand name being Prozac. The raphe nuclei, which are dotted around the brainstem, use serotonin as a transmitter when they communicate with the limbic system and frontal lobe. The limbic system is associated with emotions and memory, and the frontal lobe governs behaviour, emotions and 'higher thinking' such as planning, organising and problem solving.

The hypothalamus controls many hormones, including cortisol. Most of us have heard about how cortisol is the 'stress hormone'. The hypothalamus doesn't produce it (that is the role of the zona fasciculata of the adrenal cortex) but it does cause its secretion in response to stress and low blood sugar levels. Changed patterns of serum cortisol levels have been observed in connection with depression.  It is also believed that long-term elevated levels of cortisol can damage cells in the hippocampus, which is where many of our short term memories are consolidated into long term memory. 

In addition, the locus coeruleus which is situated in the brainstem also sends messages using the transmitter noradrenaline to the limbic system and frontal lobe.

Then there's the ventral tegmentum area. This has long axons projecting into the limbic system and frontal lobe. It does this using the neurotransmitter called dopamine.These neurotransmitter systems affect many parts of the brain.

So, is depression a consequence of abnormalities relating to serotonin, noradrenaline, dopamine or cortisol? Or does one cause the other? We don't know. 

Then there's the debate surrounding neuroplasticity, where the brain does not adapt following experiences. Whilst abnormalities of neuroplasticity have been shown in animals with major depressive disorder, it is uncertain whether this is a cause or an effect. 

Depression is frustrating because it feels like the invisible illness - not just because it may not have a physical manifestation, but to many it isn't classified as a 'real disease'. To all those who feel ashamed of being depressed, I hope you appreciate that just because your peers and society haven't found the answers to depression, that does not negate or downplay the disease. Without sounding trite, just because there isn't a fool-proof cure and explanation for cancer doesn't mean it isn't a real illness. The same goes for depression. 




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