"Depression is not a rational disease category; like cough, it is a symptom with symptoms. If we didn’t know about the range of illnesses that cause coughs, we would have no basis for understanding the “refractory cough” and we would come up with all kinds of explanations for why some cough seems to resist treatment. We do not at this time have a clear system for sorting out the different types of depression and their different implications. It is unlikely that such an illness has a single explanation. If it occurs for a whole catalog of reasons, one must use multiple systems for examining it. There is something inherently sloppy about the current modes, which take a pinch of psychoanalytic thinking and a little bit of biology and a few external circumstances and throw them together into a crazy salad. We need to disentangle depression and grief and personality and illness before we can make real sense of depressed mental states.
The most basic animal response is sensation. The experience of hunger is unpleasant and the feeling of satiety is pleasant for all living creatures, which is why we make the effort to feed ourselves. If hunger were not a disagreeable sensation, we would starve. We have instincts that lead us to food, and when those instincts are foiled—by the unavailability of food, for example—we experience extreme hunger, a condition we will do almost anything to alleviate. Sensations tend to trigger emotions: when I am unhappy about being hungry, I am having an emotional response to a sensation. It appears that insects and many invertebrates have sensation and response to sensation, and it is difficult to say where in the animal hierarchy emotion begins. Emotion is not a characteristic exclusively of the highest mammals; but it is also not an appropriate word to use in describing the behavior of an amoeba. We are afflicted with the pathetic fallacy and have an anthropomorphic tendency to say, for example, that an underwatered plant is unhappy when it droops—or, indeed, that the car is being grumpy when it keeps stalling. It is not easy to distinguish between such projections and true emotion. Is a swarm of bees angry? Is a salmon going upstream resolute? The highly regarded biologist Charles Sherrington wrote in the late forties, when he looked through a microscope at a flea biting, that “the act whether reflex or not, seemed charged with the most violent emotion. Its Lilliput scale aside, the scene compared with that of the prowling lion in Salambo. It was a glimpse suggesting a vast ocean of ‘affect’ pervading the insect world.” What Sherrington describes is how action appears to the human eye to reflect emotion.
If emotion is a more sophisticated matter than sensation, mood is a yet more sophisticated idea. The evolutionary biologist C. M. Smith describes emotion as weather (whether it’s raining out right now) and mood as climate (whether it’s a damp, rainy part of the world). Mood is a sustained emotional state that colors responses to sensation. It is made up of emotion that has acquired a life of its own quite outside of its immediate precipitants. One can be unhappy because of hunger and get into an irritable mood that will not necessarily be alleviated by eating something. Mood exists across species; in general, the more developed the species, the more powerfully mood occurs independent of immediate external circumstance. This is most true in people. Even those who do not suffer from depression have blue moods sometimes, when little things seem to be full of reminders of mortality, when those who are gone or those times that are gone are missed suddenly and profoundly, when the simple fact that we exist in a transient world seems paralyzingly sad. Sometimes people are sad for no apparent reason at all. And even those who are frequently depressed sometimes experience high moods when the sun seems extra bright and everything tastes delicious and the world is explosively full of possibilities, when the past seems like just a little overture to the splendor of the present and the future. Why this should be so is both a biochemical and an evolutionary puzzle. The selective advantages of emotion are much easier to see than the species’ need for mood.
Is depression a derangement, like cancer, or can it be defensive, like nausea? Evolutionists argue that it occurs much too often to be a simple dysfunction. It seems likely that the capacity for depression entails mechanisms that at some stage served a reproductive advantage. Four possibilities can be adduced from this. Each is at least partially true. The first is that depression served a purpose in evolution’s prehuman times that it no longer serves. The second is that the stresses of modern life are incompatible with the brains we have evolved, and that depression is the consequence of our doing what we did not evolve to do. The third is that depression serves a useful function unto itself in human societies, that it’s sometimes a good thing for people to be depressed. The last is that the genes and consequent biological structures that are implicated in depression are also implicated in other, more useful behaviors or feelings—that depression is a secondary result of a useful variant in brain physiology.
The idea that depression at one time served a useful function that it no longer serves—that it is in effect a relic—is borne out by our many vestigial emotional responses. As the psychologist Jack Kahn has pointed out, “People do not have a natural fear of real dangers like cars and light sockets, but waste their time and energy being afraid of harmless spiders and snakes”—animals it would have been useful to fear in a different time at a different stage of our development as a species. Following this pattern, depression often clusters around what seem to be utterly unimportant matters. Anthony Stevens and John Price have proposed that some form of depression is necessary for the formation of primitive rank societies. Though lower organisms and some higher mammals, such as the orangutan, are loners, most advanced animals form social groupings, which furnish better defense against predators, better access to resources, greater and more accessible reproductive opportunities, and the prospect of cooperative hunting. There is no doubt that natural selection has favored collectivity. The impulse toward collectivity is extremely strong in human beings. We inhabit societies and most of us rely heavily on the sense of belonging. Being well liked is one of life’s great pleasures; being excluded, ignored, or in some other way unpopular is one of the worst experiences we can have.
If a lower-ranking animal challenges the leader and doesn’t get discouraged, he will keep challenging the leader and there will be no peace and the group will not be able to function as a group. If, upon losing, such an animal stops being self-assertive and withdraws into a somewhat depressed state (one characterized more by passivity than by existential crisis), he thereby acknowledges the winner’s triumph, and he accepts perforce the dominance structure. This subdominant figure, by yielding to authority, frees the winner from the obligation to kill him or to expel him from the group. So through the appropriate occurrence of mild to moderate depression, social consonance can be achieved in a rank-based society. That those who have suffered depression frequently relapse may indicate that those who have fought and lost ought to avoid fighting again, so minimizing damage to themselves. The evolutionist J. Birtchnell has said that brain centers are constantly monitoring one’s status in relation to others, and that we all function according to internalized notions of rank. The result of a fight will determine how most animals rank themselves; depression can be useful in preventing such animals from challenging their rank when they have no real chance of improvement. Often, even if not engaged in improving social position, people suffer the criticism and attack of others. Depression pulls them out of the territory in which they are subject to such criticism; they disengage so that they do not get put down (this theory seems to me to have a bit of a sledgehammer-to-mosquito problem). The anxiety element of depression is then tied to the fear of being the object of such vigorous attack as to be excluded from the group, a development that in animal societies and in human hunter-gatherer times would have had fatal consequences.
This particular argument for the evolutionary structures of depression is not highly relevant to depression as we now experience it in societies that have enormous numbers of external structuring principles. In pack-animal societies, group structure is determined by physical strength expressed through fights in which one party triumphs over the other by diminishing or defeating it. Russell Gardner, for many years the head of the Across-Species Comparisons and Psychopathology (ASCAP) Society, has looked at how human depression is linked to animal models. He proposes that, in humans, success is less contingent on putting down others than on doing things oneself. People are not successful solely on the basis of their preventing anyone else from being a success; they succeed because of their own achievements. This is not to say that one is entirely free of the business of competition and of doing injury to others, but the competition that characterizes most human social systems is more constructive than destructive. In animal societies, the essential subject of success is “I’m stronger than you,” while in human societies it is to a greater degree “I’m fantastically good.”
Gardner proposes that while actual testable strength determines the animal social order, with those who are weak developing depression like states, in human societies, public opinion determines the social order. So while a baboon might act depressed because each of the other baboons can (and does) beat him up, a human being might become depressed because nobody thinks well of him. Still, the basic rank hypothesis is borne out by contemporary experience—people who lose rank do become depressed, and that can sometimes make them more accepting of a lower rank in society. It should be noted, nonetheless, that even those who refuse to accept lower rank are not usually thrown out of contemporary societies—some of them, indeed, become respectable revolutionaries.
Depression is an agitated cousin of hibernation, a silence and withdrawal that conserves energy, a slowing down of all systems—which seems to support the idea that depression is a relic. That depressed people long for their own bed and don’t want to leave the house evokes hibernation: an animal should hibernate not in the middle of a field but in the relative safety of its cozy den. According to one hypothesis, depression is a natural form of withdrawal that must take place in a secure context. “It may be that depression is associated with sleep,” Thomas Wehr, the sleep man at the NIMH, has suggested, “because it’s really associated with a place where sleep occurs, with being at home.” Depression may also be accompanied by altered levels of prolactin, the hormone that causes birds to sit for weeks on end on their eggs. That’s also a form of withdrawal and quiescence. Of milder depression, Wehr says, “The members of the species who were too anxious to deal with crowds, didn’t go to high places, didn’t enter tunnels, didn’t single themselves out, shied away from strangers, went home when they sensed danger—they probably lived long and had lots of babies.”
It is important to bear in mind evolution’s putative singularity of purpose. Natural selection does not wipe out disorders or move toward perfection. Natural selection favors the expression of certain genes over other genes. Our brains evolve less rapidly than our way of life. McGuire and Troisi call this the “genome-lag hypothesis.” There is no question that modern life carries burdens incompatible with the brains we have evolved. Depression may, then, well be a consequence of our doing what we did not evolve to do. “I think, in a species that’s designed to live in groups of fifty to seventy,” says Randolph Nesse, a leader in evolutionary psychology, “living in a group of several billion is just hard on everyone. But who knows? Maybe it’s diet, maybe exercise rates, maybe changes in family structure, maybe changes in mating patterns and sexual access, maybe sleep, maybe having to confront death itself as a conscious idea, maybe none of these.” James Ballenger of the Medical University of South Carolina adds, “The stimuli for anxiety just weren’t there in the past. You stayed within easy distance of home, and most people can learn to deal with one place. Modern society is anxiety-provoking.” Evolution invented a paradigm in which a particular response was useful in particular circumstances; modern life provokes that response, that constellation of symptoms, under many circumstances in which they are not useful. Rates of depression tend to be low in hunter-gatherer or purely agricultural societies; higher in industrial societies; and highest in societies in transition. This supports McGuire and Troisi’s hypothesis. There are a thousand difficulties in modern societies that more traditional societies did not have to face. Adjusting to them without having time to learn coping strategies is nearly impossible. Of these difficulties, the worst is probably chronic stress. In the wild, animals tend to have a momentary awful situation and then to resolve it by surviving or dying. Except for persistent hunger, there is no chronic stress. Wild animals do not take on jobs that they regret; do not force themselves to interact calmly, year after year, with those they dislike; do not have child custody battles.
Perhaps the primary source of the extremely high level of stress in our society is not these evident afflictions but the freedom offered us in the form of an overwhelming number of uninformed choices. The Dutch psychologist J. H. van den Berg, who published his The Changing Nature of Manin 1961, argues that different societies have different systems of motivation and that each era requires a new round of theory—so that what Freud wrote may well have been true of human beings of the late nineteenth and early twentieth centuries in Vienna and London, but was no longer necessarily true of human beings in the mid–twentieth century, nor was it ever strictly true of people in Peking. Van den Berg suggests that there is no such thing as informed choice about way of life in modern culture. He speaks of the invisibility of the professions, whose continuing diversification has resulted in an array of possibilities that is beyond comprehension. In preindustrial societies, a child could walk through his village and see the adults at work. He tended to choose (where choice was operative at all) his own job on the basis of a fairly thorough understanding of what each of the available options entailed—what it was to be a blacksmith, a miller, or a baker. Perhaps the details of the life of the priest were unclear, but the way of life of the priest was fully visible. This is simply not true in postindustrial society. Few people have understood since childhood what exactly a hedge-fund manager or a health-care administrator or an associate professor actually does, or what it is like for him to do it.
The realm of the personal is the same. Up until the nineteenth century, one’s social options were limited. With the exception of a few adventurers and heretics, people grew up and died in the same place. They were held in rigid class structures. A tenant farmer in Shropshire had few options about whom to marry: he chose among the women who were of the right age and class in his locale. Perhaps the one he truly loved proved unavailable and he had to settle for someone else, but at least he’d reviewed the options, knew what he might have done, and knew what he was doing. Members of the upper classes occupied a world that was somewhat less geographically constricted but was numerically small. They too tended to know all the people whom they might have the opportunity to marry and to be aware of the full range of their options. This is not to say that cross-class marriages did not take place, or that people did not move from one spot to another, but such gestures were infrequent and reflected a conscious disavowal of convention. Highly structured societies that do not present unlimited opportunity may engender acceptance of one’s lot in life, at least in a relatively large percentage of the population—though of course a full acceptance of one’s situation achieved through introspection is rare in any society in any time. With the development of better transportation, the growth of cities, and the advent of class mobility, the range of possible mates suddenly swelled to immeasurable proportions. The people who in the mid–eighteenth century could say that they had reviewed all available members of the opposite sex and chosen the fairest have been forced in more recent times to settle for the less comforting assurance that they have chosen the best of those with whom they happen to have come in contact so far. Most of us will meet thousands of other people in our lifetimes. So loss of the basic assurance—of feeling one knows whether one had chosen the right profession and of feeling that one knows whether one had chosen the right spouse—has left us bereft. We cannot accept that we simply don’t know what to do; we cling to the idea that one should make choices on the basis of knowledge.
In political terms, freedom is often burdensome, which is why transitions out of dictatorship often cause depression. In personal terms, slavery and excessive freedom are both oppressive realities, and while some part of the world is paralyzed by the narrow despair of inescapable poverty, the more developed nations are paralyzed by the very mobility of their populations, by the twenty-first-century nomadism of constantly pulling up roots and resettling to accommodate jobs and relationships and even fancy. A writer addressing this problem tells the story of a boy whose family had moved five times in a short period, who hanged himself from an oak in the backyard, leaving a note pinned to the tree that said, “This is the only thing around here that has any roots.” The feeling of perpetual disruption holds for the jetting executive who visits thirty countries in an average year, and the middle-class city dweller whose job keeps getting redescribed as his company is bought out time and again and who does not know from year to year who will work for him or for whom he will work, or for the person who lives alone and encounters different checkout staff every time he goes grocery shopping. In 1957, an average American supermarket had sixty-five items in the produce section: shoppers knew what all the fruits and vegetables were and had had each of them before. In 1997, an average American supermarket had over three hundred items in the produce section, with many markets pushing a thousand. You are in the realm of uncertainty even when you select your own dinner. This kind of escalation of choices is not convenient; it is dizzying. When similar choices present themselves in every area—where you live, what you do, what you buy, whom you marry—the result is a collective uneasiness that explains much, in my view, about the rising rates of depression in the industrialized world.
Further, we live in an era of dazzling, bewildering technologies, and we have no concrete grasp of how most of the things around us work. How does a microwave function? What is a silicon chip? How do you genetically engineer corn? How does my voice travel when I use a cell phone as opposed to a regular phone? Is it real money that a bank machine in Kuwait deducts from my account in New York? One can research any of these particular questions, but to learn the answers to all the small science questions of our lives is an overwhelming task. Even for someone who understands how the motor of a car works and where electricity comes from, the actual mechanics of daily life have become increasingly obscure.
There are many specific stresses for which we are ill prepared. The breakdown of the family is certainly one, and the advent of the solitary life is another. The loss of contact, and sometimes intimacy, between working mothers and their children is another. Living a working life that entails no physical movement or exercise is another. Living in artificial light is another. Loss of the comforts of religion is yet another. Incorporating the explosion of information in our age is yet another. The list can be expanded almost indefinitely. How could our brains be prepared to process and tolerate all this? Why wouldn’t it be a strain for them?
Many scientists have subscribed to the idea that depression serves a useful function in our society as it exists today. Evolutionists would want to see that the presence of depression favors the reproduction of certain genes—but if one looks at the reproductive rates of depressives, one finds that depression in fact decreases reproduction. Like physical pain, depression is intended to warn us off certain dangerous activities or behaviors by making them too unpleasant to tolerate so it is the capacityfor depression that is most obviously useful. Paul J. Watson and Paul Andrews, evolutionary psychiatrists, have proposed that depression is actually a means of communication and have modeled evolutionary scenarios according to which depression is a social disease, one that exists for its interpersonal role. Mild depression, in their view, causes intense introspection and self-examination, on the basis of which it is possible to make sophisticated decisions about how to effect changes in one’s life so that it better suits one’s character. Such depression can be and often is kept secret, and its function is private. Anxiety—distress in advance of an event—is often a component of depression and can be useful in preventing trouble. Mild depression—low mood that has taken on a life separate from the triggering circumstance—can motivate a return to what had been foolishly cast off, valued only after its loss. It can cause one to regret true mistakes, and to avoid making them again. Life decisions often follow the old rule of investments: high-risk decisions may bring high rewards, but at a cost that is potentially too high for most people. A situation in which a person cannot disengage from a truly hopeless goal may be resolved through depression, which forces disengagement. People who pursue their goals with excessive tenacity and cannot relinquish attachments that are evidently unwise are especially subject to depression. “They’re trying to do something interpersonally that’s not going to succeed, but they can’t give up because they are so emotionally overinvested,” Randolph Nesse says. Low mood serves to delimit persistence.
Depression can certainly interdict behaviors that have negative effects we might otherwise tolerate. Excessive levels of stress, for example, cause depression, and the depression may cause us to avoid the stress. Too little sleep may lead to depression, and depression can throw us back to more sleep. Among the primary functions of depression is changing nonproductive behaviors. Depression is often a sign that resources are being poorly invested and need to be refocused. Practical examples of this abound in modern life. I heard of a woman who had been trying to make her way in the world as a professional violinist, despite the discouragements of her teachers and colleagues, and who suffered from an acute depression that was only minimally responsive to medication and other therapies. When she gave up music and switched her energies to an area to which her abilities were better suited, her depression lifted. Paralyzing though it feels, depression can be a motivator.
More serious depression may arouse the attention and support of others. Watson and Andrews suggest that pretending one needs help from others does not necessarily secure that help: others are too smart to be deluded by phony neediness. Depression is a convenient mechanism because it supplies the convincing reality: if you’re depressed, then you really are helpless, and if you really are helpless, you may be able to extort assistance from others. Depression is a costly form of communication, but it is all the more compelling because it is so costly. It is the sincere horror of it that gets others motivated, so say Watson and Andrews; the dysfunction caused by the onset of depression may serve a useful function in that it is “a device for the elicitation of altruism.” It may also convince those who are responsible for causing you difficulties to leave you alone.
My depression brought out all kinds of helping behaviors in my family and friends. I received a much higher level of attention than I might otherwise have expected, and those around me took measures to relieve certain burdens—financial, emotional, and behavioral. I was freed of all kinds of obligations to friends because I was simply too sick to come through for them. I stopped working: I had no choice about that. I even used my illness to get permission to delay payment of my bills, and various pesky folk were obliged to stop bothering me. Indeed, when I had my third depressive episode, I took an extension on the completion of this book and did so with absolute certainty; fragile though I may have felt, I was able to state categorically that no, I could not just go on working anyway, and that my situation would have to be accommodated.
The evolutionary psychologist Edward Hagen sees depression as a power play: it involves the withdrawal of one’s services to others until they accommodate one’s needs. I disagree. The depressed make lots of demands on people around them, but then—if they weren’t depressed, they wouldn’t need to make all those demands. The chances of those demands being fully met are relatively slender. Depression can be a useful blackmail, but it is generally too unpleasant for the blackmailer and too inconsistent in its results to be a well-selected way of achieving specific ends. Though it can be gratifying to get support when you are feeling dreadful, can indeed help to build a depth of love that would otherwise be unimaginable, it is much better not to feel so dreadful and not to need so much support. No—I believe that low mood serves the function of physical pain in causing one to avoid certain behaviors because of unpleasant consequences, but the voguish idea that depression is a means to accomplish social goals makes little sense to me. If major depression is nature’s strategy for making independent beings seek help, it’s a risky strategy at best. The fact is that most people are appalled by depression. Though some respond to a display of depression with increased sympathy and altruism, more respond with revulsion and disgust. It is not unusual to discover in a depression that people you had believed were reliable are actually unreliable—a valuable piece of information you might have preferred not to have. My depressions have sorted the wheat from the chaff among my friends, but at how high a cost? And is it worth forsaking other relationships that give me pleasure simply because they were not reliable in a terrible time? What kind of a friend should I be to such people? How much of friendship is about being reliable anyway? How does being reliable in a crisis relate to being kind or generous or good?
The idea that depression is the misfiring of mechanisms that also serve useful functions is perhaps the most convincing of all the evolutionary theories. Depression most frequently stems from, and represents an aberrant form of, grief. It is not possible to understand melancholia apart from mourning: the basic pattern of depression exists in sorrow. Depression may be a useful mechanism that gets stuck. We have a range of heart rates to allow us to function in varying circumstances and climates. Real depression is, like a heart that doesn’t pump blood to the fingers and toes, an extreme in which there is virtually no inherent advantage.
Grief is profoundly important to the human condition. I believe that its most important function is in the formation of attachment. If we did not suffer enough loss to fear it, we could not love intensely. The experience of love incorporates sadness into its intensity and range. One’s wish not to injure those whom one loves—indeed, to help them—also serves the preservation of the species. Love keeps us alive when we recognize the difficulties of the world. If we had developed self-consciousness and not developed love as well, we would not long tolerate the slings and arrows of life. I’ve never seen a controlled study, but I believe that people with the greatest capacity to love are more likely to cleave to life, to remain alive, than those without it; they are more likely also to be loved, and that too keeps them alive. “A lot of people would see heaven as a place where there would be infinite intensity and variety,” Kay Jamison has said. “Not a place that is trouble-free. You would want to eliminate some extremes, but not to cut the spectrum in half. There’s a very fine line between saying that you want people to suffer and saying you don’t want people to be denied emotional range.” To love is to be vulnerable; to reject or decry vulnerability is to refuse love.
Crucially, love prevents us from abandoning our attachments too readily. We are made to agonize if we walk out on the people whom we truly love. Perhaps the anticipation of grief is critical to the formation of emotional attachments. It is the contemplation of loss that makes one hold tight to what one has. If there were no despair after the loss of someone, one would spend time and emotional energy on that person only as long as it was pleasurable to do so, and not one minute longer. “Evolutionary theory,” says Nesse, “is generally thought to be a cynical practice. Evolutionary biologists interpret all the complexity of moral behavior as though it were simply a system for the selfish benefit of one’s own genes. Of course much of one’s behavior is explicitly for that purpose. But often one’s actions lie outside of these parameters.” Nesse’s field of study is commitment. “Animals cannot make complex contingent promises about the future to one another. They cannot bargain and say, ‘If you will do this for me in the future, then I will do this for you.’ A commitment is a promise in the present to do something in the future that may not be in your best interests at that time. Most of us live by such commitments. Hobbes saw this. He understood that our capacity for such commitments is what makes us human.”
The capacity to make commitments is to the evolutionary advantage of one’s genes; it is the basis of the stable family unit that provides the ideal environment for the young. But once we have that capacity, which serves an evolutionary advantage, we can use it in any way we choose; and in these choices lies the moral compass of the human animal. “People’s reductive notions of science have caused us to see relationships mostly as mutual manipulations and mutual exploitations,” says Nesse, “but in fact feelings of love and hate often extend to the impractical. They don’t fit with our rationalistic system at all. The capacity for love may serve an evolutionary advantage, but how we act in the face of love is a process of our own. The superego pushes us to do things that give benefit to others at the cost of our own pleasure.” It invites us into the realm of moral alternatives, a realm that loses its meaning if we try to eliminate grief and its milder sad cousin, regret. Some insects are born from untended egg sacs with a lifetime food supply intact; they need sexual impulse, but not love. The precursors of attachment, however, exist even in the world of reptiles and birds. The instinct to sit on an egg and keep it warm—in contrast to laying an egg and then sauntering off and leaving it to get cold, be crushed, or be devoured by passing animals—clearly enhances reproductivity. In most postreptilian species, mothers who feed their young, as good birds do, have more young who survive, and this enhances their success in producing little chicks who will grow into big birds and procreate. The first emotion, and one for which selection would most significantly occur, is a version of what we call love between a mother and her young. It seems likely that love emerged among the first mammals and that it motivated these creatures to care for the relatively helpless young born without an eggshell into the threatening world.''
Andrew Solomon
