"Stress has become more commonplace and accepted in our everyday lives," says Sonia J. Lupien, PhD, lead author and director of the Laboratory of Stress Research at the Douglas. "Many studies show the negative impact of stress on physical health such as blood pressure, heart disease etc, but few address the effects on mental health. Our studies look directly at the long term effects of stress, or stress hormones, on brain function."

Lupien and colleagues measured the stress hormone, cortisol, in older adults over a period of three to six years. Their findings showed that individuals who had continuous high levels of cortisol, performed poorly on memory tests and had a notably smaller hippocampus, the part of the brain responsible for learning and memory.

"This study clearly shows the negative effects of long-term stress," says Lupien. "This explains why some older adults show poor brain function while others perform very well. Perhaps, through early interventions, we can modify the cortisol levels and enhance brain function of the at-risk individuals. "

Lupien and her research team also looked at the affects of stress on young adults and children between the ages of six and fourteen. In young adults, they showed that even an acute increase in cortisol can lead to reversible memory impairments. In young children, they compared the cortisol levels of children from low and high socioceconomic status (SES) and found children from low SES had higher cortisol levels.

"Similar to our findings with the older adult, stress was an important modulator of brain function in children as well," says Lupien. "All these studies show that people of all ages are sensitive to stress, and we need to acknowledge the importance of this factor on our mental health."