Does the client on your table see the glass half empty or half full? The answer could determine how much cortisol is surging through his body.

A study that looked at adults’ ability to respond to stressful events has found that optimists are better able to meet life’s challenges than are pessimists.

Study participants were asked to report on the level of stress they experienced in their day-to-day lives, and to self-identify along a continuum as optimists or pessimists. Each person’s stress levels were then measured against their own average.

“Measuring the stress levels against participants’ own average provided a real-world picture of how individuals handle stress because individuals can become accustomed to the typical amount of stress in their lives,” noted a press releases from Concordia University’s Department of Psychology.

Pessimists tend to have a higher stress baseline than optimists, but also have trouble regulating their system when they go through particularly stressful situations, said study co-author Joelle Jobin, a Ph.D. candidate in clinical psychology.

“On days where they experience higher than average stress, that’s when we see that the pessimists’ stress response is much elevated, and they have trouble bringing their cortisol levels back down,” Jobin said. Optimists, by contrast, were protected in these circumstances, she added.