Unlike a physical ailment, which is visible to the eyes, the actual reasons that trigger depression inside the closed chambers of the human mind are yet to be ascertained.
There have been disagreements among researchers on the causes that lead to depression. Also, the fact that the nature of depression varies from one person to another makes the matter worse. However, there are a number of broadly agreed upon reasons whose combined effect results in depression.
1. Genetic causes of Depression.
The risk of depression increases manifold in people who have a family history of depression. Research has shown us that more than 4,000 diseases can be caused by the genetic depression variants. For example, children born to a parent with depressive tendencies or having siblings exhibiting the same traits will have almost 50% chance of developing depression later in their lives.
2. Circadian Rhythm.
The internal master biological clock plays a vital role in orchestrating the circadian rhythms of multiple biological processes. A disturbed circadian rhythm over a long period of time can lead to depression.
3. Illness-induced Depression.
It is estimated that up to 35% of people suffering from a major illness experience symptoms of depression. Depression caused by chronic illness can in turn worsen the ailment, triggering a vicious cycle to develop.
4. Biochemical causes of Depression.
Every cell communicates with each other by engaging the neurotransmitters Dopamine, which helps to control the brain’s reward and pleasure centers and Serotonin that helps in managing our well being and happiness. If the Dopamine and Serotonin levels are imbalanced, the transmission from one cell to another becomes hazy and if this continues for long, it can lead to brain fog resulting in chronic fatigue, fibromyalgia, stress and ultimately depression.
5. Chronic Stress.
If not handled well, stressful life situations sustained over a period of time can increase the risk of developing depression. In sustained stress, the body keeps producing the stress hormone cortisol, restraining the smooth working of bodily functions.
6. Emotional causes of Depression.
More than 90% of our ailments are partly stress induced psychosomatic illnesses. The human brain processes around 12,000 to 50,000 random thoughts – good or bad – in a day. Therefore, distorted thinking on a daily basis can turn a simple thought or emotion into an experience of depression.
7. Personality induced causes of Depression.
People with low self-esteem or overly self-critical personality styles are more prone to get affected by depression. Some of the personality styles that can cause depressions are the anxious-worrying-irritable personality style, self-critical personality style, self-absorbed and perfectionist personality style, socially avoidant and personally reserved personality style and rejection sensitive personality style.
8. Other causes of Depression.
Being bullied, death in the family or of a close friend, setbacks in career and finances, failing a critical exam at school and substance abuse also leads to depression. We often don’t pay proper attention to or ignore these causes, but they too can culminate in chronic depression at some point in our lives.
 Depression; a global physical and mental killer
 A few signs and symptoms of Depression
 Science behind Depression: Biology of a Dark Mind
 Managing Depression without Medication
 Yoga helps ease Depression