An interesting study followed 1600 men over a total of 18 years, tracking how neurotic they were, whether they got worse of better over time, and assessed their mortality risks.  

At the conclusion of the study,  Purdue University psychologist Daniel Mroczek found, "those who increased over time in neuroticism was a ticket to an early grave. In other words, these men-all middle age or older to begin with-did not grow old gracefully. They likely got more and more stressed, worried or fretful, and this downward spiral increased their risk for dying, mostly from cancer and heart disease."