What’s more, optimists are likely to take good care of their bodies, because they believe that their choices will make a difference. Pessimists are prone to junk food and no exercise, as they believe it won’t matter.

On the other hand, pessimism  can likely be a cause of depression . Believing that nothing you do will change anything can of course make you depressed. A study where people had to press buttons to make noises stop found symptoms of depression in them whenever the experiment was rigged so that the buttons had no effect.