We can all compare before and after pictures of presidents and know the presidencies ages the person who holds the office. Here is a piece on the health risks of being president. Here is one of the factors considered:
Severe, sustained stress
Although the record has improved recently -- Reagan lived to 93, while President Ford is 91 and President George H.W. Bush 80 -- Northeastern University professor Robert Gilbert notes that more than two-thirds of presidents have failed to reach their era's life expectancy for white males, "despite the fact that they have received the best medical care that you can imagine."
Post says a "certain degree of stress" can make people "more alert, more focused" during a crisis, "but the data on sustained stress shows a decrease in functioning over time, even though a person may believe he is at the height of his powers."
In the long run, Post says, "stress tends to bring out not the best in people, but magnifies the flaws that are already there."
President Coolidge, for example, suffered from severe depression after his son's death, which historians link to his administration's record.
Oftentimes, the office's many demands can impair a president's mental health.
As the Watergate crisis unfolded, several leading senators alerted Brown -- one of Washington's top mental health experts -- about President Nixon's "withdrawal of social contact" and rumors of increased drinking. Nixon showed paranoid tendencies, as did his predecessor Lyndon Johnson related to rising antiwar sentiment, "that put terrible strains on them," Boston University professor Robert Dallek says.