“Essentially, we humans live well enough and long enough, and are smart enough, to generate all sorts of stressful events purely in our heads.”

Modern humans living in developed civilizations are more prone to experiencing psychological and social stressors rather than physical stressors, such as running from predators. Sapolsky implies that intelligence is what leads to psychological stress, with the implication that intelligence is not universally beneficial.

“It is never really the case that stress makes you sick, or even increases your risk of being sick. Stress increases your risk of getting diseases that make you sick, or if you have such a disease, stress increases the risk of your defenses being overwhelmed by the disease.”

Sapolsky explores The Biology and Effects of Stress, clarifying that stress, in itself, does not make a person sick. Instead, it creates vulnerability to diseases and their respective symptoms. By highlighting this concept, Sapolsky prevents spreading the sensational idea that stress causes disease. The information is also critical to comprehending more complex ideas, including the variable susceptibility between individuals and the lack of definitive medical answers for how stress results in poor health.

“As the master gland, the brain can experience or think of something stressful and activate components of the stress-response hormonally.”

This statement provides a simplified synopsis of one way in which psychological stressors trigger the sympathetic nervous system. Both thoughts and hormones originate in the brain, which creates an inextricable link between the endocrine and nervous systems. Synopses, such as this, offer condensed, easy-to-digest information, which reflects the intended lay-reader audience (See: Background).