The Biology Behind Anxiety and Depression


Mental health disorders are a major problem affecting overall public health, with 1 in 4 people diagnosed with some form of mental illness.

Of these disorders, anxiety and depression are considered the two most common, often being diagnosed together. In fact, roughly 50% of patients diagnosed with depression are also diagnosed with anxiety, representing 9.7% of the overall public.

Depression is mainly highlighted as a mental disorder that induces helplessness and hopelessness in its victims, eliciting the self-damaging symptoms, such as loss of interest and a decrease in energy. It was frequently believed that depression resulted from a chemical imbalance in the brain, with those experiencing depression expected to exhibit lower levels of chemicals, such as the “happy chemical” Serotonin, compared to their healthy counterparts.

However, more recent research into this disorder has highlighted that depression is perhaps more complex than this simple chemical imbalance.

It was demonstrated that patients diagnosed with depression also exhibited defects in their hippocampus, such as a decrease in size and lack of cellular growth. The hippocampus itself is a key part of the limbic system, which functions in the processing and control of emotion, learning and memory. Such defects were therefore translated as the biological cause of the symptoms experienced by these patients.

Anxiety arises as an issue revolved around the fear of the unknown, with the role of this emotion to increase the individual’s awareness in order to prepare them for any harmful scenarios. Anxiety is a normal human emotion, with it being a key determinant of the fight-or-flight response. However, when this emotion is prolonged, its effects are felt more intensely for longer periods of time, producing anxiety disorders.

Credit: Mackenzie Brown

Interestingly, like depression, the feeling of anxiety is controlled by the limbic system, with certain parts of this system, such as the amygdala and hippocampus, playing important roles in the onset of this emotion. The amygdala functions in the communication between sensory signals, such as sight, and the interpretation of this signal based on previous experience. From this, it develops the correct emotional response based on this interpretation, one being the initiation of the anxiety response.

It is believed that the basis of any anxiety disorder relates to a dysfunction in this processing ability of the amygdala. Patients may then lack the ability to differentiate a threat from other normal situations, explaining the abnormal initiation of the anxiety response in these patients.

Unfortunately, the current biological explanations for these disorders only provide a short glimpse into the severity and complexity of mental health. Current knowledge is forever adapting, with the exact causes and cures changing, not only over time but also between each individual. Mental health is still a major problem of the modern world, highlighting the need for more research into the nature of mental health in order to fully understand this problem.



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