Daniel Gilbert, author of Stumbling on Happiness, wrote this post about how uncertainty increases tendency to worry. From the post:
...researchers at the University of British Columbia studied people who had undergone genetic testing to determine their risk for developing the neurodegenerative disorder known as Huntington’s disease. Those who learned that they had a very high likelihood of developing the condition were happier a year after testing than those who did not learn what their risk was.
Why would we prefer to know the worst than to suspect it? Because when we get bad news we weep for a while, and then get busy making the best of it. We change our behavior, we change our attitudes... But we can’t come to terms with circumstances whose terms we don’t yet know. An uncertain future leaves us stranded in an unhappy present with nothing to do but wait.
What Gilbert says makes a lot of sense.