Introduction

Picture the following scenario (Figure 12.1). Two students are jogging at dusk along a fire trail in the Berkeley, California hills. As they approach a small grove of trees, they spot a mountain lion lurking in the shadows. The students freeze. They can feel their hearts pounding, their breath quickening, their muscles are tense, their palms sweaty. All they can see is the mountain lion as it crouches and prepares to attack. The students turn towards the mountain lion, waving their arms and creating noise in an attempt to ward it off. They hurl strewn rocks until the mountain lion finally retreats.

Weeks later, one of the students keeps remembering the encounter and experiencing distress, is having trouble sleeping and no longer wants to jog in the hills. The other does not show signs of distress after the initial shock.

Encountering a mountain lion ready to attack would be a very stressful event for most people. A pounding heart, shallow breathing and sweaty palms are all part of the body’s response to stress—an adaptive response which ensures our survival by preparing us to fight, flee or freeze in the face of threat. In the aftermath of this stressful encounter, why does one student experience lasting effects while the other has none?

In this chapter you will learn about stress and the stress response, the mechanisms regulating it, how stress affects brain circuits and behavior, and what sets up the variability between people in how they respond to stress.