Researchers from Concordia University in Canada tracked 135 older adults over six years, and collected their saliva samples five times a day to monitor cortisol levels.
This age group was selected because older adults often face a number of age-related stressors and their cortisol levels have been shown to increase.
Participants were asked to report on the level of stress they perceived in their day-to-day lives, and self-identify along a continuum as optimists or pessimists. Each person's stress levels were then measured against their own average.
Joelle Jobin, a PhD candidate in clinical psychology who co-authored the study with her supervisor Carsten Wrosch and Michael Scheier from Carnegie Mellon University, noted that pessimists tended to have a higher stress baseline than optimists, but also had trouble regulating their system when they go through particularly stressful situations.
More From This Section
"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. Optimists, by contrast, were protected in these circumstances," said Jobin.
Jobin said there are several possible explanations, but also noted that the finding points to the difficulty of classifying these complex hormones as good or bad.
"The problem with cortisol is that we call it 'the stress hormone', but it's also our 'get up and do things' hormone, so we may secrete more if engaged and focused on what's happening," Jobin said.