Up until about 10 years ago, having a conversation about mental health was almost unheard of. In recent years, mental health has become a more open topic and is now seen as less of a taboo, with it featuring on news reports, at the centre of research and being spoken about on social media platforms.  However, mental health still remains a dominant problem in todays society, with statistics surrounding it constantly increasing. Maybe the key to tackling mental health is to stop merely talking about it, and actually educate people on the causes of it. 

Lets start with depression…

Depression is the most predominant mental health problem worldwide and, along with anxiety, has been estimated to cause one fifth of workplace absences in the UK. Nowadays, we can assume that most people know what depression is and the symptoms of it, however, if you were to ask the ‘average Joe’, what the causes of depression are, the chances are that the majority wouldn’t know. 

According to psychologists, the cause of depression can be attributed to many factors: genetics, upbringing, life events etc, however, for the purposes of this pathway, we are going to concentrate on the biological, or neurological causes of depression. There are three regions of the brain that have been linked to depression:

  1. Amygdala – the amygdala makes up part of the limbic system or, according to Steve Peters work, our ‘chimp’, and is associated with emotion. When a person is sad or clinically depressed, the activity in the amygdala is higher than normal, and this increased activity continues even after we stop feeling sad, or have overcome depression. 
  1. Hippocampus – the hippocampus, again is part of our limbic system. This part of the brain plays a central role in processing long-term memory and recollection. The hippocampus and the amygdala work together, creating associations between our memories and the emotions that come with them. For example, if you were to come across a barking, aggressive dog, the amygdala would register feelings of fear, and then when we come next across a dog, our hippocampus tells us that we should be wary of it because we have previously experienced fear when near one. It has been found that in people who are depressed, the hippocampus is 9%-13% smaller compared to people who are not depressed. 
  1. Thalamus – the thalamus is responsible for receiving sensory information from our environment and relaying that information to other parts of the brain, which help to produce high-level functions such as speech, behavioural reactions, movement and learning. The thalamus helps the brain link sensory input to pleasant and unpleasant feelings. 


Neurotransmitters are chemicals that assist with the relay of messages between our nerve cells or neurons, in our brain. When someone has depression, the rate that these messages are relayed slows, and therefore, the level of neurotransmitters going to the amygdala, hippocampus and thalamus decreases. There are a number of neurotransmitters that are believed to play a role in depression: acetylcholine, norepinephrine, dopamine, GABA to name a few. However, the neurotransmitter that seems to be at the forefront of all research into this area is serotonin. Serotonin helps to regulate sleep, appetite, mood, and inhibits pain. When serotonin is released into our brains, we feel valued, significant and influential. This makes us feel confident and assured. It has been found that those with depression have lower levels of serotonin in their brains, explaining why changes in sleeping patterns and appetite are symptoms of depression. 

When someone is feeling sad or low, less serotonin is released into their brains as they aren’t necessarily feeling valued or significant. If these feelings of sadness continue, even less serotonin is being released and therefore, our mood is affected on a long-term basis. This is what can cause depression. To help overcome these feelings of depression, it would make sense that we try to increase our serotonin levels. Depending on how depressed a person is, this can be done through self-help methods, such as exercise, change in diet and mindfulness techniques; psychological treatments such as Cognitive Behavioural Therapy (CBT); or through medication. 

To help us better understand the causes of depression, we are going to focus on medication as a treatment for depression. 


At present, the main pharmaceutical treatment for severe depression is a type of anti-depressant medication called Selective Serotonin Reuptake Inhibitors (SSRIs). As well as depression, SSRI’s are used to treat numerous mental health conditions, including generalised anxiety disorders panic disorder, and phobias. The function of SSRI’s is to increase the amount of serotonin in the brain. They do this by inhibiting the reuptake of serotonin of the brain.

Look at the diagram below. Imagine the blue diamonds are serotonin, and the orange circle is the amygdala. Normally, the serotonin travels to the amygdala, it is ‘reuptaked’ and then travels to another part of the brain.  


Because people who are depressed have lower levels of serotonin, the amount of serotonin to reuptake is less than that of a person without depression, therefore, the areas of the brain that regulate our mood, such as the amygdala, have even lower levels of serotonin, affecting our mood, and this cycle continues. 

SSRI’s prevent this reuptake from happening, so the level of serotonin in the areas of the brain that need it, remains at a constant level, increasing the person’s mood.  


From this we can conclude that although the causes of depression aren’t restricted to the decrease in neurotransmitters in the brain, we can use this explanation to educate people that depression is actually caused by a physical thing, rather than labelling it as a ‘mental’ illness that people don’t fully understand. Explaining it in this way, ‘normalises’ it, and actually provides an answer to the question, ‘why do you have depression?’.  

In Summary: the awareness surrounding mental health is increasing all the time, however, there is still a lack of understanding into the causes of it. Although we cannot pin point the cause to biological reasons alone, explaining the physical changes that happen within our brains when someone is depressed, can actually provide people with an explanation as to why they’re feeling the way there are, and make mental illnesses such as depression seem more ‘normal’. 

Final points to takeaway

If you feel you are struggling with your mental health (or if you aren’t!) remember the following: 

  • Understanding the causes of mental illness is key to tackling the stigma surrounding it
  • Although this pathway focuses on depression, remember that physical causes can play a role in all mental health conditions 
  • Mental health is normal 
  • Mental health can be attributed to physical causes
  • Not feeling yourself? Speak to someone: friends, family, colleagues or your GP. 
  • People will understand. If they don’t, make them read this! 

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