I don't think this is true.
A good mental health is not about not having an emotional problems (this can't be prevented, for example sadness due to a death of a close person can't be prevented and might serve a purpose of leading to acceptance), but about being able to deal with them without falling into serious disorders.
It would be an "a.effective secondary source document" that best describes a chart developed 20 years after a historical event, since the information as had time to "settle"--although of course this doesn't automatically mean that the chart is "effective".