Following groups of children through life is one of the more interesting
things that researchers do -- usually with the intention of improving public
health, welfare and education policies.

An American study that began in 1921 with the aim of identifying the
intellectual achievers of the future has now, nine decades later, yielded
another kind of information: which childhood characteristics and experiences
are likely to extend a person’s life or shorten it. These results have just
been published in a book, The Longevity Project, by Howard S Friedman and
Leslie R. Martin.

Lauro Landro reports
in The Wall Street Journal:

There are no magic potions on offer here, but many of the findings are
provocative. The best childhood predictor of longevity, it turns out, is a
quality best defined as conscientiousness: "the often complex pattern of
persistence, prudence, hard work, close involvement with friends and
communities" that produces a well-organized person who is "somewhat
obsessive and not at all carefree."

The original researcher, Stanford University psychologist Lewis Terman,
asked teachers to select their brightest students (most were around the age of
10) but having a high IQ did not seem to play a direct role in longevity:

Neither did going on to an advanced degree. The authors suggest that
persistence and the ability to navigate life's challenges were better
predictors of longevity.

Fortunately, Terman’s questionnaires were very detailed and picked up all
sorts of things about the students’ lives and later development. So, eight
decades later it was also possible to see what things tend to shorten a person’s
life, and there was one particularly strong family factor:

Some of the findings in "The Longevity Project" are surprising,
others are troubling. Cheerful children, alas, turned out to be shorter-lived
than their more sober classmates. The early death of a parent had no measurable
effect on children's life spans or mortality risk, but the long-term health
effects of broken families were often devastating. Parental divorce during
childhood emerged as the single strongest predictor of early death in adulthood.
The grown children of divorced parents died almost five years earlier, on
average, than children from intact families. The causes of death ranged from
accidents and violence to cancer, heart attack and stroke. Parental break-ups
remain, the authors say, among the most traumatic and harmful events for
children.

The world has changed a lot since those 1500 children grew up, matured and
died, and they were a very select group to start with -- all white and
middle-class, for starters -- but even given the limitations, the links
Friedman and Martin have discovered are worth considering:

…The respondents to the study who fared best in the longevity sweepstakes
tended to have a fairly high level of physical activity, a habit of giving back
to the community, a thriving and long-running career, and a healthy marriage
and family life. They summoned resilience against reverses and challenges—
including divorce, loss of a spouse, career upsets and war trauma. By contrast,
those with the darkest dispositions—catastrophizers, who viewed every stumble
as a calamity—were most likely to die sooner…

The bad news about cheerful kids is a bit hard to swallow, but it seemed to
be linked with recklessness later in life. Perhaps it depends on what you mean
by “cheerful”. Friedman and Martin suggest that this finding underlines the
importance of cultivating forethought and purposefulness in children.

One can be conscientious and still be cheerful, surely.