Evolutionary Psychiatry: Broadening the Scope of Clinical Understanding

Dan J. Stein, MD, PhD

Professor and Chair of Psychiatry, University of Cape Town, Cape Town, South Africa

This interview was conducted by Peter Cook on April 28, 2006.

Introduction

Dr. Dan J. Stein, who is Professor and Chair of Psychiatry at the University of Cape Town, South Africa, has researched and written extensively on different anxiety disorders, including OCD, SAD, and PTSD. It would seem obvious that anxiety is an important survival mechanism, and this has led him to take some interest in the relevance of evolutionary theory to psychiatry. He recently published a brief but exhaustive overview of the interface between evolutionary theory and psychiatry titled “Evolutionary Theory, Psychiatry, and Psychopharmacology,” and an editorial titled “Evolutionary Psychiatry: Integrating Evolutionary Theory and Modern Psychiatry.” Although he admits that the clinical relevance of this work is not always immediately apparent, Dr. Stein believes that such work does have merit, and he hopes it will contribute increasingly to clinical care and future research.

History

Whereas much of biological psychiatry focuses on the proximate mechanisms underlying illness, evolutionary psychiatry is particularly interested in the distal (evolutionary) causes of behavior and psychiatric pathology. The discipline grew out of evolutionary psychology, which truly began with Charles Darwin, who attempted to apply his theory of natural selection to human behavior. Prior to Darwin, this was considered the product of cultural and/or divine influences; after Darwin it was possible to consider the adaptive origins of animal and human behavior. Ethologists in the mid-20th century applied the tenets of evolutionary theory to animal behavior with remarkable success, and a number of its practitioners (eg, Konrad Lorenz) examined psychiatric problems using ethological principles.

It was not until 1975, however, when E.O. Wilson wrote his controversial book “Sociobiology, the New Synthesis,” that the idea that even the most complex human behaviors were rooted in evolutionary theory gained widespread academic attention. This attention was, however, often quite negative; many accused Wilson of championing “eugenics,” and even the less vituperative were worried that his theories could be used to justify prejudice and sexism. The charges were ill made, as Wilson was not attempting to justify wrongdoing, but merely to place human behavior in a larger evolutionary context. However, it took quite some time for the furor to die down, and recently, “sociobiology” has reappeared under the moniker “evolutionary psychology” to more widespread academic acceptance.

Current Research and Application

“People talk about proximal and distal mechanisms in underlying psychopathology,” Dr. Stein says, “but most of what we learn in medical school is the proximal or biological mechanism. For example, anxiety is mediated by the amygdala. Now, the evolutionary approach examines the distal question: Why did the amygdala come into being in the first place? And why have circuits in the amygdala persisted over time?” Nesse and Williams’ book “Why We Get Sick” was important for bringing ideas of evolutionary theory into general medicine. They believed that a full understanding of a pathology required a distal understanding of the problem: did it arise from a defect (eg, seizures), defense (eg, pain), or dysregulation of defense (eg, dehydration from diarrhea).

Dr. Stein warns that evolutionary questions, while interesting, can lead to a proliferation of “just-so stories”—distal explanations for behavior that cannot be tested and that may just reflect the ideology or agenda of whoever comes up with them. However, Dr. Stein believes it is possible to approach evolutionary psychiatry with scientific rigor. “It’s fine to come up with a distal story,” he says, “but it needs to be based in brain science. At times we can form a small distal hypothesis that’s actually testable, such as the idea that infanticide is more commonly at the hands of step-parents than by biological parents, and this is increasingly what’s being done.” He cites recent work on aggression, attachment, mothering, theory of mind, emotion, personality, and a whole slew of other psychiatric concepts. More and more relevant research is being done on specific disorders as well.

From the standpoint of evolutionary psychiatry, there are several ways to look at the origins of a psychiatric disorder, and it can be difficult to determine which view is correct. “Take anxiety,” Dr. Stein says. “We could posit that anxiety is a survival mechanism, that it’s adaptive. Many types of anxiety responses might actually produce healthy behavior. On this argument, it may be useful to have a degree of social anxiety; this protects us in potentially dangerous social situations. Alternately, we might suggest that anxiety was, at one point in human evolution, adaptive, but is no longer so. Many doctors view obesity in this light: When fatty, carbohydrate-loaded foods were rare, it was adaptive to find them very appealing. Now that they’re everywhere, our appetite for these foods seems to have become maladaptive. A similar argument might apply to specific phobias for small animals—which aren’t commonly dangerous in our urban environments. In some sense, evolution hasn’t caught up to our current environment yet. Lastly, you have to consider that some disorders may just the product of defects or of bad luck—take OCD. It’s easy to imagine that some degree of obsessiveness could, under certain circumstances, be selected for, but it’s difficult to imagine how spending hours each day on an obsession could be selected for in any environment. Sometimes the body just doesn’t work like it’s supposed to.”

Treatment

“Generally,” Dr. Stein says, “when you’re dealing with symptoms, treatment will be based on our understanding of proximal mechanisms, so distal explanations don’t usually impact on management.” There are, however, exceptions. He points out that an understanding of some psychological response as adaptive could well impact how a clinician chooses to treat the patient. “If the symptoms you’re treating actually have some functional value—as opposed to being true dysfunctions—you should be extra cautious. Various temperaments such, as a hypothymic temperament, may be adaptive, and one would want to be aware of the potential costs of treatment therefore. However, Dr. Stein notes that it’s a mistake to conflate the notion of what is evolutionary adaptive with what is diagnosed as a clinical problem. “Natural selection works on genes,” he says. “Psychiatrists work on people.”

One direct application to practice is in educating patients about their symptoms.

“Explaining patients’ difficulties to them in terms of evolutionary maladaptions can help many patients stop blaming themselves for their problems,” Dr. Stein says.

Conclusion

“It’s not clear that understanding distal mechanisms will immediately lead to changes in treatment,” Dr. Stein says. “But they do contribute to conceptual changes, and conceptual changes can have impact. A clinician conversant in evolutionary psychiatry might be more willing to examine the adaptive value of certain symptoms. At the very least, he or she will have a better understanding of the context of psychiatric disorders.”

Disclosure: Dr. Stein has received grant support/honoraria from AstraZeneca, Eli Lilly, GlaxoSmithKline, Lundbeck A/S, Orion, Pfizer, Pharmacia, Roche, Servier, Solvay, Sumitomo, and Wyeth.