Did You Ruminate Your Way
One of the causes of depression is the tendency or habit to over-ruminate. Rumination refers to the act of mulling over things, turning them over and over in the mind.
The problem with rumination
Rumination over something that has gone wrong seems to be a natural human instinct. This instinct could be adaptive – a little dwelling could lead to valuable insights and greater clarity on what went wrong, what can be done to correct the situation, and what could help prevent similar negative situations from arising in the future. 
Nonetheless, when the rumination becomes extended, not only does it become a waste of time (since one is unlikely to achieve any more new insights on the matter), it can also become harmful as it amplifies negative emotions and increases feelings of stress.
In fact, those who have a tendency or habit to engage in extended periods of rumination are actually more vulnerable to depression. Through amplifying negative emotions on an extended basis, prolonged rumination can actually start the body’s stress response circuits up on the runaway (i.e. excessive, uncontrolled and extended) mode – a trigger for depression. 
The impact of rumination
Rumination isn’t just one of the important causes of depression. It is also a key factor in maintaining depression in sufferers.
This is because rumination can also negatively impact one’s behavior. The inward focused process of rumination (especially when carried out on a habitual basis) can lead people to become less active, more withdrawn, and less sociable. This is because it is hard to focus on the external world and give attention to another while ruminating. 
Subsequently, relationships could be affected. In addition, the withdrawal and inactivity arising from excessive rumination can also deprive depression sufferers of a sense of competence, productivity and achievement. Yet such a sense of self-efficacy is so important for the depressed that cognitive-behaviorist Peter McLean noted that “the most powerful antidepressant is successful performance”. 
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