Many people express this behavior due to the indirect expression of emotions such as displeasure, frustration, and anger. This occurs mainly due to environmental factors during their childhood. In this case, they never felt safe to express their emotions. As a result, they opt for this behavior as a means of expressing their emotions.  In other cases, people express this behavior due to an underlying medical condition that promotes this behavior. Some of these health conditions include Schizotypal personality disorder, Bipolar disorder, Depression, Stress, and ADHD (Attention Deficit Hyperactivity Disorder).