In the year before a “big” birthday (at age 29, 39, 49 and so on) people tend to ruminate more than at other times on the meaning of life, according to a study published Monday in the Proceedings of the National Academy of Sciences (PNAS).
No surprise there, perhaps. But the study also found that when people’s age ends in a 9, they are also significantly more likely to engage in new behaviors that reflect “an ongoing or failed search for meaning,” such as running a marathon or having an extramarital affair, than when their age ends in a different digit.
Most troubling, however, was the finding that “9-enders” are at an increased risk of commiting suicide.
“People are more apt to evaluate their lives as a chronological decade ends, and, as a result, more likely to make life-altering decisions,” note the study’s authors, Adam Alter of New York University and Hal Hershfield of the University of California, Los Angeles, in a released statement. “As we age, it’s good to understand this propensity so we’re more likely to make constructive rather than destructive choices.”
A series of studies
The PNAS paper actually describes a series of six studies conducted by Alter and Hershfield. For two of the studies, the researchers analyzed data collected from more than 42,000 adults in 100-plus countries who had participated in the World Values Survey. The survey asked people, among other things, how often they questioned the meaning and purpose of life. While most of the respondents said they thought about such things often, the “9-enders” did so more frequently than any of the respondents whose ages ended in another digit.
In a third study, Alter and Hershfield examined data on more than 8 million men who had registered on a dating website designed for people seeking affairs outside of their current marriages or relationships. They found that more than 950,000 of the men were age 29, 39, 49, or 59 — a number that was 18 percent higher than might be expected by chance alone.
Next, the researchers looked at 2000-2011 suicide data from the U.S. Centers for Disease Control and Prevention (CDC). They found that the suicide rate was slightly higher (2.4 percent) for individuals whose age ended in a 9 than for people whose age ended in any other digit.
More productive behavior
“Having shown that 9-enders were more likely to engage in two behaviors that suggested a crisis of meaning, we next considered whether 9-enders also tend to engage in productive meaning-seeking behavior,” write Alter and Hershfield. For this part of their research they decided to look at the ages of non-elite marathon runners, because, they say, the marathon represents “a particularly meaningful athletic challenge.”
Using data from Athlinks, a website that collects finishing times for people running marathons and other races, Alter and Hershfield found that runners ran, on average, a statistically significant 2 percent faster during races they finished at age 29 or 39 than during races they completed two years before and after those ages. Faster times, note Alter and Hershfield, “tend to suggest that runners have trained harder or are more motivated.”
The researchers then looked at a random selection of 500 first-time marathon runners, aged 25 to 64. They found that 74 of those runners were 9-enders — an overrepresentation of 48 percent.
Together, these six studies show “that 9-enders are particularly preoccupied with aging and meaningfulness, which is linked to a rise in behaviors that suggest a search for or crisis of meaning,” Alter and Hershfield conclude. “Although some of these effects were small, they occur in domains with consequential life outcomes.”
You’ll find an abstract of their paper on the PNAS website.