There is a small part of the brain - amygdala, which lights up every time the brain is informed there is 'something wrong'. It may be the politicians on tv quarreling or the noise of the street waking us up in the middle of night. Every time stress hormones are released which prepare the body to fight the danger or flight from it. If the signal is temporary, it's not so bad, it's a stress response mechanism that was intended from nature. The problem starts when the mechanism becomes chronic, then we have chronic stress. For example if we watch the politicians quarreling and threatening one another every day for a long time, the amygdala is active all the time telling 'there is something wrong', get ready to 'fight or flight'. Obviously this chronic stress mechanism wears down the brain and the body and in long term causes various health problems.