To better understand the overall impact of neuroticism, in and of itself, on society, the researchers looked at about 5,500 adults drawn from the general population. They looked at their medical costs and the amount of days they were absent from work to come up with an annual figure (in dollars). They assessed neurotic traits using a 14-item scale crafted from a personality inventory questionnaire used widely in the Netherlands.

The researchers found that the average costs for people who scored in the top 5 percent based on neuroticism were $12,362 over and above the average for the population. Excess costs for people in the top 10 percent were $8,243, while costs for the 25 percent who scored the highest on neuroticism were $5,572.