What causes Depression?

I personally believe in the biopsychosocial model of Depression which suggests that Depression is multifactorial and depends on a bunch of biological, psychological, and social factors.

Biology of Depression
In terms of biology the story goes like this. Stress, genetics, habits, and a disruption of communication between prefrontal cortex and the limbic system contribute to bringing on an episode of Depression. Your genes are responsible for making you vulnerable to Depression whereas stress triggers the genes to express themselves and manifest the illness. Bad habits play a role in perpetuating an episode of Depression. Once the neural circuitry of Depression is engraved in the brain, probability of relapse skyrockets.

Isn’t Depression caused by a lack of Serotonin in the brain?
One popular hypothesis for cause of Depression is the lack of certain neurotransmitters in the brain such as Serotonin, Norepinephrine, and Dopamine. This is a chicken or the egg situation. Did the lack of these neurotransmitters cause Depression or is the reduction in the levels of these neurotransmitters simply a symptom of Depression? Antidepressants work by increasing the levels of Serotonin and Norepinephrine in the brain (depending on the class of antidepressants). The good news is that antidepressants seem to work for 30-40% of the patients. The bad news is that they don’t work for the remaining 60-70% of the patients. Another puzzling fact is that even though the antidepressants boost neurotransmitter levels in the brain within hours of taking the medication, the patients don’t see a relief in symptoms for at least six to eight weeks. This eludes to the fact that there may be something more at play within the brain than simply boosting neurotransmitter levels.
Understanding the functions of various neurotransmitters does help understand the various symptoms of Depression. Serotonin, for example, regulates sleep, mood, appetite, and decision making. So, a lack of Serotonin would explain the symptoms of disturbed sleep, low mood, reduced or increased appetite, and the indecisiveness that accompanies Depression. Similarly, norepinephrine regulates focus and concentration which explains their lack of in Depression. Dopamine regulates the reward and pleasure circuits in the brain which explains one of the most common symptoms of Depression, anhedonia, which is a lack of pleasure in activities. GABA regulates emotional responses to various situations and promotes relaxation. Low levels of GABA may cause anxiety, panic attacks, irritability, and the inability to fall and stay asleep. Endorphins are opioid like substances released in the brain after intense exercise that lead to a sense of wellbeing and relief from physical pain aka, the runners high. A lack of endorphins resulting from inactivity accompanying Depression explains the symptoms of chronic pain. It sounds like there is some correlation between Depression and the lack of certain neurotransmitters but this neurotransmitter story seems incomplete. More research is required in this field to obtain a better understanding of the biology of Depression.

Psychology of Depression

The psychology of Depression is well understood by most people. From a psychological perspective, Depression is characterized by excessive focus on the negative feelings, thoughts, body sensations, and memories and a lack of appreciation for the positive feelings, thoughts, and events in life. Some might say that the tendency or the habit of focusing on the negative can cause Depression. Excessive worry, rumination, thinking in endless loops, obsessive-compulsive thoughts, lack of meaning and purpose in life are all deemed to cause Depression. In my opinion, it isn’t so much the negative thoughts, obsessive compulsive thoughts or any other unpleasant thoughts, feelings, or sensations that cause Depression. It is rather the struggle with the negative and the constant effort exerted to get rid of the negative in our lives that can potentially sink one into Depression.

Social causes of Depression

Some common social triggers that can lead to Depression and perpetuate the illness are as follows:
– Loss of a loved one
– Lack of necessities for survival such as food, shelter, and clothing
– Lack of meaningful work
– Lack of meaningful relationships
– Lack of purpose in life
– Living in an overly materialistic culture and society
– Constant comparison of your status and achievements with others
– Childhood trauma or abuse
– Lost status or low status in society

Depression can result from a combination of the various biological, social, and psychological factors mentioned above. In my opinion, a large majority of the cases of Depression in our society today are a result of social and psychological causes. The materially focussed society we live in today and the society’s aversion to freely express unpleasant emotions can wreak havoc on our psychology. It is my opinion that a very small percentage of cases of Depression is a result of biological dysfunction. Is it possible that Depression is not a biological illness at all? Why is it that to this date we don’t have any means of diagnosing Depression from biological markers in the body? Food for thought.

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