For their study they analyzed data on over 2,000 American ex-military personnel aged 55 and over from the National Health and Resilience in Veterans Study, a nationally representative survey of the 9 million or so older veterans. The survey collected a range of data, including measures of mental health, attitudes, and social activity.
They found that of the participants with the most positive attitude toward aging, only 2% had post-traumatic stress disorder compared with 19% of those with the most negative attitude. They also found similar differences for experiencing suicidal thoughts (5% compared with 30%) and anxiety (4% compared with 35%).
The researchers also found the same link between resistance to negative age stereotypes and lower rates of psychiatric conditions in non-combat veterans and say this suggests the same is likely to be true of older people in general.