Understanding the etiology of mental disorders from a biological perspective can be at times difficult. There is no wonder research is still being undergone nowadays to further understand the underlying reasons for certain conditions. However, it needs to be noted how outstanding progress has been made from the past up to today. The brain is a complex network involving several pathways that are implicated in distinct tasks such as behavior, memory, perception, or emotions, and those depending on how are managed by our brain circuitry which implies chemistry can in turn be involved in mental disorders.

 There is more scientific knowledge in certain mental conditions than in others, the reason behind this is that the understanding of how the brain works have not been yet fully discovered. To partially understand the role of brain mechanisms in mental disorders we need to first know what neurotransmitters are; these are chemical messengers that are used for communication between neurons and they can either be excitatory, modulatory, or inhibitory. There are also several different types of neurotransmitters and each is involved in different aspects.

• Dopamine: involved in the movement, reward response, motivation, mood, sleep and arousal, behavior, and cognition.
• Serotonin: or (5-hydroxytryptamine, 5-HT), is highly involved in body temperature modulation, emotions, sleep cycle, pain perception, mood, and sexual function.
• GABA: or (gamma-Aminobutyric acid), is very much related to mood regulation and emotions.
• Adrenaline: or (epinephrine), is involved in the fight or flight response, it can increase blood pressure as well as heart rate.
• Acetylcholine: or (ACh), is highly involved in muscle contraction and plays a role while we are asleep.
• Endorphins: are highly involved in feeling well (pleasure), as well as pain and stress reduction. These are the body’s natural pain relievers.
• Oxytocin: highly involved in sexual arousal, and attachment, and facilitates face recognition.
• Glutamate: plays an important role in memory and learning processes.
• Histamine: as a primary inflammatory response, however, it has many other functions such as sexual behavior, and wakefulness regulation, and is capable of decreasing blood pressure.
• Norepinephrine: or (noradrenaline), involved in wakefulness and alertness, stress reaction, attention, and fight or flight response.
• Vasopressin: or (antidiuretic hormone, ADH), is involved in wakefulness, sleep, body temperature, and even behavior.

Now that we understand more or less how neurotransmitters work, we can continue to describe certain mental health conditions and their biological functioning.

Depression is a serious medical condition that has been increasing among individuals in the modern world. There are three neurotransmitters so far that are thought to play a role in depression, those are dopamine, norepinephrine, and serotonin. In the case of dopamine, as we have previously seen, it plays a role in motivation and the reward system, and this, in turn, is what makes us pursue certain activities, in patients with depression we can see that they lack motivation and this is because dopamine levels are decreased. Furthermore, serotonin is involved in how we feel and in our mood, and having low levels of serotonin can affect these aspects of depressive-like symptoms. Finally, norepinephrine since it is involved in the fight or flight response is also decreased in most patients with depression which explains why they might have lethargic and fatigue-like symptoms.

Similarly, some neurotransmitters that are thought to have an impact on depression also seem to co-occur with anxiety disorders, those include norepinephrine, serotonin, and dopamine. Another neurotransmitter that does not seem to be present in depression but does in anxiety disorders is gamma-aminobutyric acid. Interestingly, in the case of serotonin, low levels of this neurotransmitter which is also seen in depressive patients are thought to also be present in anxiety conditions. On the other hand, norepinephrine levels seem to be high in anxiety disorders and it makes sense since this neurotransmitter is involved in the fight or flight response. In most patients with anxiety disorders, their dopamine levels tend to be high, furthermore, imbalances in GABA are highly common in anxiety disorders.

There is considerable evidence through empirical research on how neurotransmitters imbalances of a certain type can affect and are present in mental disorders, however, there is controversy on the imbalances whether the levels are high or low because certain individuals show different results from others, this means that further research is needed to improve our understanding in this issue, furthermore, the scientific information we can obtain from research is promising in terms of explaining how there is an actual physiological explanation for mental disorders.

By Marta Padron Pena, Mental Health Intern

References:

 https://www.kenhub.com/en/library/anatomy/neurotransmitters

https://my.clevelandclinic.org/health/articles/22581-dopamine

https://www.verywellmind.com/the-chemistry-of-depression-1065137

https://www.verywellmind.com/is-panic-disorder-caused-by-a-chemical-imbalance-2583984