Why Zebras Don’t Get Ulcers, by Robert Sapolsky

In this humorous and informative book, Robert Sapolsky explains how and why stress affects our bodies. The premise is that prey animals like zebras use a stress response in an evolutionary sensible way by upping certain hormones while they are being hunted, but then the zebras’ stress levels drop again when they escape. Humans have the same bodily changes, only our stress tends to be small amounts for long periods of time, meaning the effects on the nervous system (lower digestion, higher blood pressure, reduced growth, etc.) remain continuously activated. Therefore, human stress is not sensible from an evolutionary standpoint. Each chapter in Sapolsky’s book covers a different bodily system and explains in detail how and why stress affects it. He ends with a rather lengthy description of how lower socio-economic status affects our bodies. Although this section was interesting, it seemed a bit lengthy and out of place from the rest of the book. The subject could be a book all on its own. 

One thing I loved about this book is it’s approachability. It was easy to read and made me laugh several times each chapter. Sapolsky has an excellent dry sense of humor. He also included a picture of baboons smack in the middle of his book for seemingly no reason. That made me laugh as well. 

I was listening to his companion set of lectures Stress and Your Body concurrently, though I dropped behind and still have several lectures yet to finish of the course. You can see some details of the information covered in the book and lectures if you check out the above link. In hindsight, although both were enjoyable, only one or the other was necessary as most of the material was exactly the same – even to the wording. 

This is a very stressful book to read, so watch out if you are prone to stress. 

(For another theory about why stress evolved, you can check out my review of the Noonday Demon by Andrew Solomon). 

Stress and Your Body: An introduction

Great Courses: Stress and Your Body, by Professor Robert Saplosky,
narrated by Robert Saplosky
Robert Saplosky is a professor of biological sciences, neurology, and neurosurgery at Stanford University. His lab focuses on how stress affects the nervous system. He also has extensive field work, studying a particular population of wild baboons in East Africa – where he examines how social rank, personality, and sociality affect vulnerability to stress-related disease. He is a fantastic lecturer, and if you get the chance to watch a YouTube video of him lecturing, go for it. 

Saplosky and The Teaching Company developed the course Stress and Your Body to teach us about the detrimental effects of stress on our health. The primary textbook is his own Why Don’t Zebras Get Ulcers? Which, as far as I can tell from chapter 1 versus lecture 1, is pretty much verbatim with his lectures.  

Remember that time you were lying in bed, worrying about the big exam, presentation, or event that might make-or-break you the next day? You couldn’t sleep because you were ruminating about the fact that if you couldn’t sleep, you’d do terribly the next day. Then you noticed some minor symptom that’s been troubling you lately. Your head’s been aching. Oh no! You have a brain tumor! Now not only can you not sleep because of your event the next day, but you’re worried about your health.

This is the type of stress that often happens to humans. We worry about things that might happen in the future, rather than worrying about things that are happening now. Thus, our stress is generally long-lasting rather than immediate and acute. 

Animals biologically respond to stressors in very similar ways to ourselves, but their reasons for being stressed vary significantly from ours. A zebra might be munching contentedly on grass until suddenly he spots a lion. His fight-or-flight response ramps up. A part of his autonomic nervous system (responsible for controlling unconscious bodily functions) called the sympathetic nervous system is activated. His body goes into energy saving mode: it turns off all the functions that are unnecessary for fight-or-flight, and turns on the ones that are. 

He saves energy. That means his stomach stops digesting, he stops producing semen, his immune system – which requires a huge amount of energy – slows way down. Tissue repair – also another drain on energy – halts.  The rate of his heart and glucose metabolism increases so that oxygen and energy flows to the limbs for fight or flight. 

He runs.

This is a very helpful response to an immediate stressor like a lion. As soon as the zebra escapes the lion, the stress is gone and the zebra contentedly starts munching on the grass again. His parasympathetic nervous system activates, reversing all the bodily changes outlined above. He’s now in rest-and-digest mode. 

When humans experience long-term stress, many of the same pathways as short-term stress are activated, leading to chronically increased blood pressure, poor digestion, dysfunctional glucose metabolism, and heightened susceptibility to infection (among many other things). Such effects on the body will be discussed in detail as we explore Saplosky’s course. 

Saplosky, Robert. (2004) Chapter 1: Why Don’t Zebras Get Ulcers? Why Don’t Zebras Get Ulcers? Third edition. (Nook ebook pp. 13-30). Holt, Henry & Company, Inc.

Saplosky, Robert. (2010) Lecture 1: Why Don’t Zebras get Ulcers? Why Do We? Stress and Your Body. The Teaching Company, The Great Courses.

Post Traumatic Stress Syndrome – the Basics

I think we all have some idea of what we think PTSD is, but it turns out PTSD isn’t as clear-cut as I thought.

Apparently, when PTSD was first introduced into the DSM, the diagnostic criteria required a traumatic event “outside the range of usual human experience” that would cause “significant symptoms of distress in almost anyone.” That fits pretty well with my own perception of PTSD. Rape, war, torture, violent experiences…these all fit into that description. PTSD is a normal response to an abnormal stressor. 

However, in the DSM-IV, the nature of the “traumatic event” broadened drastically, and a requisite response was “intense fear, helplessness, or horror.” So in the DSM-IV, PTSD was a pathological response to a potentially less extreme stressor. Someone could be diagnosed with PTSD if they experienced “intense horror or helplessness” after watching a scary TV show or upon being diagnosed with a terminal illness.

Although I don’t wish to undermine the intense stress that someone with pathological responses may feel, I think this definition undermines the intensely awful experience that someone with PTSD (in my mind) has encountered. The statistics agree with my assessment of these criteria: in a community survey, 89.6% of people reported that they had been exposed to a traumatic event and had responses that could potentially qualify them for a PTSD diagnosis.

Luckily, the DSM-5 tightened the traumatic event criteria again, and broadened the range of response to the traumatic event. Now, the traumatic event must occur directly to the subject, and they can exhibit other pathological responses besides “intense fear, helplessness, or horror.” 

To be diagnosed with PTSD by DSM-5 standards, a person must be exposed to “actual or threatened death, serious injury, or sexual violence.” They must exhibit one of the following symptoms: intrusive distressing memories of the event, distressing dreams reliving the event, dissociative reactions, intense psychological distress at cues that remind the person of the event, or marked physiological reactions to cues that remind the person of the event. Additionally, the person must persistently avoid stimuli associated with the traumatic event, have negative alterations in cognitions and moods associated with the event (e.g. distorted cognitions about the cause or consequences of the event), and alterations in arousal and reactivity (e.g. hypervigilance or angry outbursts). 

In general, people respond to trauma with decreasing pathological symptoms. In order to be diagnosed with PTSD, the patient must have experienced these negative responses for more than 1 month, otherwise they are experiencing “acute stress disorder.”

Despite the common association of PTSD with war veterans, PTSD is actually more common in women than in men – and the traumatic events are more often domestic violence or rape than war. However, a great deal of money and time has gone into research of PTSD in war veterans. 

During WWI, symptoms of PTSD were called “shell shock,” and were thought to be caused by brain hemorrhages. However, this belief slowly subsided as doctors realized that the symptoms presented themselves regardless of injury. By WWII, traumatic reactions were known as “operational fatigue” and “war neuroses,” before the terminology finally settled on “combat fatigue” during the Korean and Vietnam wars. A rigorous longitudinal study of PTSD by Smith et. al. in 2008 found that 4.3% of military personnel deployed to Iraq or Afghanistan had PTSD. Of those, the rate was higher (7.8%) in those that had experienced combat compared to those who hadn’t (1.4%). An issue that is (rightfully!) getting much attention lately is the high rate of soldier suicide. Between 2005 and 2009, more than 1,100 soldiers took their own lives – generally with a gun. 

There are several risk factors that increase the likelihood of PTSD – being female, lower social support, neuroticism, preexisting depression or anxiety, family history of depression, substance abuse, lower socioeconomic status, and race/ethnicity. (Apparently, compared to whites, African Americans and Hispanics who were evacuated from the World Trade Center in 2001 were more likely to get PTSD.) There is also a genetic factor that increases susceptibility to PTSD. Preliminary studies suggest that people with a particular form of the serotonin transporter gene may be more susceptible to PTSD than those with the “normal” form of this gene.

On the other hand, there is at least one factor that promotes resilience to traumatic events: intelligence. It’s possible that people with higher intelligence are better able to make “sense” of the event by viewing it as a larger whole. Or an intelligent person may be better able to recognize and buffer cognitive distortions such as “I deserved that,” “why should I have lived when they died?” and “If I had only done _______, this wouldn’t have happened.”

Researchers have come up with several ways to decrease likelihood of succumbing to PTSD after a traumatic event. 

Stress-inoculation training has proved successful with members of the Armed Forces. Soldiers can be exposed, through virtual reality, to the types of stressors that might occur during deployment. Thus they are better able to deal with the trauma when exposed to the events in real life.

Debriefing after a traumatic event can also be helpful. This allows the victim to process the event in a safe environment, before the details become internalized. 

Interestingly, one study showed that subjects who were exposed to a highly disturbing film were less likely to report flashbacks if they played Tetris for 10 minutes after the film than if they sat quietly for those 10 minutes. This team of researchers also showed that simply being distracted after the disturbing video was not enough to decrease flashbacks, and that doing a verbal task actually increased the number of flashbacks. So, apparently, visio-spacial tasks decrease the likelihood of intrusive flashbacks if performed immediately after the traumatic event. I’m not sure this information is particularly useful, but it’s interesting. 

As of yet, there isn’t a highly successful way to “cure” people with PTSD. Cognitive behavioral therapy, which helps the victims recognize cognitive distortions (e.g. “I deserved that,” “why should I have lived when they died?” and “If I had only done _______, this wouldn’t have happened.”), can be helpful in reducing anxiety. Antidepressant medications can alleviate some of the depression and anxiety experienced by victims. 

One up-and-coming treatment has shown promising results. Someone with PTSD can undergo prolonged exposure to the traumatic events. They can do this through repeatedly reliving the events out loud, or even by re-experiencing them through virtual reality. Unfortunately, many PTSD vitimcs drop out of such treatments because reliving the events is too difficult. However, this treatment method has proven very helpful to people who complete the process, and I hope that work in this area continues. 

This is a series of posts summarizing what I’m learning in my Abnormal Psychology course. Much of the information provided comes from reading my James N. Butcher’s textbook Abnormal Psychology. To read the other posts, follow these links: 

The Definition of Abnormal
A History of Abnormal Psychology
Abnormal Psychology in Contemporary Society
Contemporary Viewpoints on Treating Mental Illness – Biology
Contemporary Viewpoints on Treating Mental Illness – Psychology
Frontline: New Asylums
Brave New Films: This is Crazy
Clinical Mental Health Diagnosis: Biological Assessment
Clinical Mental Health Diagnosis: Psychological Assessment
Does the DSM Encourage Overmedication?
Post Traumatic Stress Syndrome – The Basics
Panic Disorder
Obsessive Compulsive Disorder
Hoarding and Body Dysmorphic Disorders
Depression – an Overview
Personality Disorders – Clusters and Dimensions
Personality Disorders – Cluster A
Personality Disorders – Cluster B
Personality Disorders – Cluster C
Biological Effects of Stress on Your Body
Somatic Symptom and Related Disorders
Dissociative Disorders
Borderline Personality Disorder
Dialectical Behavioral Therapy
Paraphilic Disorders
Gender Dysphoria – Homosexuality and Transgender
Anxiety Disorders
Bipolar Disorder – The Basics
Suicide – An Overview


Butcher, James N. Hooley, Jill M. Mineka, Susan. (2014) Chapter 5: Stress and Physical and Mental Health. Abnormal Psychology, sixteenth edition (pp. 129-161). Pearson Education Inc.