Why We Get Sick (35 page)

The genetic contributions to anxiety disorders are substantial. Most people with panic disorders have a blood relative who has the same problem, and the search is on for the responsible genes. Will these genes turn out to result from mutant genes that have not been entirely selected out? Will they turn out to have other benefits? Or will we discover that genetic susceptibility to panic is simply one end of a normal distribution, like a tendency to develop a high fever with a cold or a tendency to vomit readily? When we find specific genes that predispose to panic and other anxiety disorders, we will still need to find out why those genes exist and persist.

D
epression sometimes seems like a modern plague. After motor vehicle accidents, suicide is the second leading cause of death of young adults in North America. Nearly 10 percent of young adults in the United States have experienced an episode of serious depression. Furthermore, the rates
seem to have increased steadily in the past few decades, doubling every ten years in many industrial countries.

Depression may seem completely useless. Even apart from the risk of suicide, sitting all day morosely staring at the wall can’t get you very far. A person with severe depression typically loses interest in everything—work, friends, food, even sex. It is as if the capacities for pleasure and initiative have been turned off. Some people cry spontaneously, but others are beyond tears. Some wake every morning at 4
A.M.
and can’t get back to sleep; others sleep for twelve or fourteen hours per day. Some have delusions that they are impoverished, stupid, ugly, or dying of cancer. Almost all have low self-esteem. It seems preposterous even to consider that there should be anything adaptive associated with such symptoms. And yet depression is so frequent, and so closely related to ordinary sadness, that we must begin by asking if depression arises from a basic abnormality or if it is a dysregulation of a normal capacity.

There are many reasons to think that the capacity for sadness is an adaptive trait. A universal capacity, it is reliably elicited by certain cues, notably those that indicate a loss. The characteristics of sadness are relatively consistent across diverse cultures. The hard part is figuring out how these characteristics can be useful. The utility of happiness is not difficult to understand. Happiness makes us outgoing and gives us initiative and perseverance. But sadness? Wouldn’t we be better off without it? One test would be to find people who do not experience sadness and see if they experience any disadvantages. Or an investigator could use a drug that blocks normal sadness, a study that we fear may soon be conducted inadvertently on a massive scale as more and more people take the new psychoactive drugs. While we wait for such studies to be done, the characteristics of sadness and the situations that arouse it provide clues that may help us to discover its functions.

The losses that cause sadness are losses of reproductive resources. Whether of money, a mate, reputation, health, relatives, or friends, the loss is always of some resource that would have increased reproductive success through most of human evolution. How can a loss be an adaptive challenge, a situation that would benefit from a special state of preparation? A loss signals that you may have been doing something maladaptive. If sadness somehow changes our behavior so as to stop current losses or prevent future ones, this would be helpful indeed.

How can people behave differently after a loss in a way that increases fitness? First, you should stop what you are doing. Just as pain can make us let go of a hot potato, sadness motivates us to stop current activities that may be causing losses. Second, it would be wise to set aside the usual human tendency to optimism. Recent studies have found that most of us consistently overestimate our abilities and our effectiveness. This tendency to optimism helps us to succeed in social competition, where bluffing is routine, and also keeps us pursuing important strategies and relationships even at times when they are not paying off. After a loss, however, we must take off the rose-colored glasses in order to reassess our goals and strategies more objectively.

In addition to sudden losses, there are situations in which an essential resource is simply not available despite major expenditures and our best plans and efforts. Jobs end, friendships fade, marriages sour, and goals must be abandoned. At some point one must give up on a major life project in order to use the resources to start something else. Such giving up should not be done lightly. Quitting one’s job shouldn’t be done impulsively, because there are costs involved in retraining and starting at the bottom of another hierarchy. Likewise, it is foolish to casually give up any important relationship or life goal in which a major investment has already been made. So we don’t usually make major life changes quickly. “Low mood” keeps us from jumping precipitously to escape temporary difficulties, but as difficulties continue and grow and our life’s energies are progressively wasted, this emotion helps to disengage us from a hopeless enterprise so that we can consider alternatives. Therapists have long known that many depressions go away only after a person finally gives up some long-sought goal and turns his or her energies in another direction.

The capacity for high and low mood seems to be a mechanism for adjusting the allocation of resources as a function of the propitiousness of current opportunities. If there is little hope of payoff, it is best to sit tight rather than to waste energy. Real estate agents who enter the business during an economic downturn may be making a mistake. Students who are failing a course would sometimes do best to drop it and try another subject. Farmers who plant their fields during a drought may go broke. If, by contrast, we come upon a short-lived opportunity, then it may be best to make a major, intense effort, despite the possible risks, in order to have a chance at a big payoff. When a million dollars in cash fell out of the back of an armored car
on the streets of Detroit, a few people who made an intense, brief effort profited nicely.

A better understanding of the functions of sadness will soon be essential. We are fast gaining the capacity to adjust mood as we choose. Each new generation of psychotropic drugs has increasing power and specificity with fewer side effects. Decades ago there was a hue and cry about “soma,” the fictional drug that made people tolerate tedious lives in Aldous Huxley’s
Brave New World
. Now that similar substances loom as a reality, strangely little is being said. Do people not realize how fast this train is moving? We certainly should try to relieve human suffering, but is it wise to eliminate normal low mood? Many people intuitively feel it is wrong to use drugs to change mood artificially, but they will have a hard time arguing against the use of nonaddicting drugs with few side effects. The only medical reason not to use such drugs is if they interfere with some useful capacity. Soon—very soon—people will be clamoring to know when sadness is useful and when it is not. An evolutionary approach provides a foundation for addressing these questions.

We are aware that this analysis is vastly oversimplified. People are not controlled by some internal calculator that crudely motivates them to maximize their reproductive success. Instead, people form deep, lifelong emotional attachments and experience loves and hates that shape their lives. They have religious beliefs that guide their behavior, and they have idiosyncratic goals and ambitions. They have networks of friends and relatives. Human reproductive resources are not like the squirrel’s cache of nuts. They are, instead, constantly changing states of intricate social systems. All these complexities do not undercut our simple arguments; they just highlight the urgency of blazing the trail of functional understanding that the adaptationist program may provide for human emotions.

While some low mood is normal, some is clearly pathological. The causes of such pathology are complex. Genetic factors are important determinants of manic-depressive disorder, a condition in which mood swings wildly from the depths of depression to aggressive euphoria. Having one parent with manic-depressive disorder increases your risk of that disorder by a factor of 5, and having two parents increases it by a factor of 10 to a likelihood of nearly 30 percent. These genes are not rare—manic-depressive illness occurs in 1 out of 200 people. Our next, by now familiar, question is, Why are these genes maintained in the gene pool? The answer is equally familiar: They
probably offer some advantage, either in certain circumstances or in combination with certain other genes. A study by Nancy Andreasen, professor of psychiatry at the University of Iowa, found that 80 percent of the faculty at the renowned Iowa Writer’s Workshop had experienced some kind of mood disorder. Is creativity a benefit of the genes that cause depression? The disease wreaks havoc in some individual lives, but the genes that cause it seem nonetheless to offer a fitness advantage either to some people with the disorder or to other people in whom the gene does not cause the disorder but has other, beneficial effects.

John Hartung, an evolutionary researcher at the State University of New York, has suggested that depression is common in people whose abilities threaten their superiors. If a person with lower status demonstrates his or her full abilities, this is likely to bring attack from the more powerful superior. The best protection, Hartung suggests, is to conceal your abilities and to deceive yourself about them so as to more readily conceal your ambitions. This could well explain some otherwise mysterious cases of low self-esteem in successful people. Hartung’s theory reminds us of the complexity of human emotions.

Another major effort to understand mood has come from a group of researchers who are pursuing British psychiatrist John Price’s theory of the role of mood in human status hierarchies. They have argued that depression often results when a person is unable to win a hierarchy battle and yet refuses to yield to the more powerful person. They suggest that depression is an involuntary signal of submissiveness that decreases the likelihood of attacks by dominants. In case studies they describe how submitting voluntarily can end depression.

UCLA researchers Michael Raleigh and Michael McGuire have found a brain mechanism that connects mood and status. In studies of vervet monkeys, they found that the highest-ranking (alpha) male in each group had levels of a neurotransmitter (serotonin) that were twice as high as those of other males. When these “alpha” males lost their position, their serotonin levels immediately fell and they huddled and rocked and refused food, looking for all the world like depressed humans. These behaviors were prevented by the administration of antidepressants, such as Prozac, that raise serotonin levels. Even more astounding, if the researchers removed the alpha male from a group and gave antidepressants to some other randomly chosen male, that individual became the new alpha male in every instance. These studies suggest that the serotonin system may function,
in part, to mediate status hierarchies and that some low mood may be a normal part of status competitions. If this is so, one cannot help but wonder what will happen in large corporations as more and more depressed employees start taking antidepressants.

Still another approach to understanding depression is based on the increase of the state that occurs when the amount of daylight decreases in the fall. The large number of people affected with this seasonal affective disorder (SAD) and its strong association with cold climates have suggested to many researchers that low mood may be a variant or remnant of a hibernation response in some remote ancestor. The preponderance of women with SAD has suggested that the response may somehow regulate reproduction.

Are there novel aspects of our modern environment that make depression and suicide more likely? While every age seems to have believed that people are not as happy as they were in earlier times, some recent evidence suggests that we may actually be in an epidemic of depression. A team of distinguished investigators looked at data from 39,000 people in nine different studies carried out in five diverse areas of the world and found that young people in each country are far more likely than their elders to have experienced an episode of major depression. Furthermore, the rates were higher in societies with higher degrees of economic development. Much remains to be done to confirm this finding, but it justifies an intense study of novel aspects of modern life that might contribute to dramatic increases in depression. We will mention only two: mass communications and the disintegration of communities.

Mass communications, especially television and movies, effectively make us all one competitive group even as they destroy our more intimate social networks. Competition is no longer within a group of fifty or a hundred relatives and close associates, but among five billion people. You may be the best tennis player at your club, but you are probably not the best in your city and are almost certainly not the best in your country or planet. People turn almost every activity into a competition, whether it be running, singing, fishing, sailing, seducing, painting, or even bird watching. In the ancestral environment you would have had a good chance at being best at something. Even if you were not the best, your group would likely value your skills. Now we all compete with those who are the best in all the world.

Watching these successful people on television arouses envy. Envy probably was useful to motivate our ancestors to strive for
what others could obtain. Now few of us can achieve the goals envy sets for us, and none of us can achieve the fantasy lives we see on television. The beautiful, handsome, rich, kind, loving, brave, wise, creative, powerful, brilliant heroes we see on the screen are out of this world. Our own wives and husbands, fathers and mothers, sons and daughters can seem profoundly inadequate by comparison. So we are dissatisfied with them and even more dissatisfied with ourselves. Extensive studies by psychologist Douglas Kenrick have shown that after being exposed to photos or stories about desirable potential mates, people decrease their ratings of commitment to their current partners.