What If Mental Illnesses Aren’t Illnesses?

Mental illness might have evolved to prevent suicide.

Two beliefs about mental illness are widely accepted and rarely questioned, both among the public and professional psychologists. First, it is generally accepted that mental illnesses are illnesses. If someone has depression, there is something wrong with their mind that has caused it to stop functioning correctly, just as cirrhosis of the liver causes the liver to stop functioning correctly. For this reason, the DSM, the principal authority for psychiatric diagnoses in the USA, uses terms like “disorder,” “dysfunction,” and “disability” to describe psychic phenomena like depression or schizophrenia. The second belief is that mental illness causes enhanced risk of suicide. Overall, the commonsensical theory goes that mental illness is a sickening of the mind, and one negative effect of this sickening is that it might lead to suicide.

C. A. Soper, an English psychotherapist and psychologist, believes that this story is fundamentally wrong and mixes up cause and effect. On Soper’s view, the evolutionary rationale for the phenomena that we call “depression,” “schizophrenia,” “bipolar disorder,” and other illnesses, is that they protect us from suicide. Many of the symptoms that are exhibited in these psychic phenomena are adaptations that prevent someone experiencing terrible pain from killing themselves.¹

In support of this view, Soper weaves a fascinating story about how the problem of suicide affected human evolution. From this story, Soper derives a rich and far-reaching theory not only of mental illness, but also of happiness, religion, and other human traits and practices. Soper’s theory is new, and much of what he says is speculative. However, it is worth understanding and researching further because, if it is true, it would have profound consequences for the way that we interpret mental illness and treat the mentally ill, as well as for our overall understanding of human nature.

Soper begins with the question of why suicide is a human universal. There is and has been no known human society that is exempt from suicide. Such ubiquity is puzzling because suicide is obviously maladaptive: if you kill yourself, you can’t have children or care for them. Natural selection, therefore, normally removes the genes for maladaptive traits from the gene pool.

Human universals are generally either adaptations, or traits that evolved to increase our biological fitness, or byproducts of adaptations, which are consequences of adaptations that do not increase fitness. The heart is an adaptation that keeps us alive by pumping blood. The heart also makes a thumping sound. That sound is irrelevant to our fitness and is hence not an adaptation. It is a by-product of the adaptive function of the heart.

Soper thinks that suicide is the by-product of two human adaptations: high intelligence and pain. He calls his theory the “pain-and-brain” theory of suicide. On the brain side, suicide is a problem that afflicts only highly intelligent organisms. A suicide is someone who knowingly causes their own death. To commit suicide then, an organism must understand what death is and how to cause their own. For this reason, no animal can commit suicide, as no animal has a concept of death. Small children cannot commit suicide either for the same reason. Humans only begin to understand death in adolescence, and it is then that suicides become possible.

The other adaptation that produces suicide as a by-product is pain, which evolved to protect us from threats to our body and mind. Suicide is tempting for us because it is a cure for unbearable pain. While physical pain can be a motive for suicide, Soper focuses on psychological or spiritual pain, like shame, guilt, humiliation, loneliness, fear, and angst, which he collectively calls “psychache.” Psychological research has found that these various forms of psychache are precursors to mental illness.

These facts in hand, Soper formulates a stunning hypothesis about human evolution: suicide would have been a temptation for our hominid ancestors as soon as they became intelligent enough to conceive of the act. Any proto-human experiencing the anguish of rejection, ostracism, or loss would have seen in suicide an easy way of making the pain stop. Soper speculates that suicide places a ceiling on the intelligence of most animals. Most apes didn’t evolve an intelligence comparable to ours because once suicide becomes possible, it is such an attractive option.

So the temptation of suicide was a major problem that evolution had to solve if highly intelligent proto-humans were to survive. Soper believes that many aspects of normal human psychology and culture are designed to keep us from killing ourselves. These include a disposition to be happy, a disposition to religious belief, self-enhancing illusions, and stigmatization of suicide. However, if all of these fail to supply us with a reason to live, there is one final defense against suicide, and that is mental illness.

Soper uses soccer as a metaphor for his theory. Usually, soccer defenders, whom Soper calls “fenders,” prevent the ball from getting near the goal. Such fenders are the anti-suicide defenses of normal psychology, like religion and happiness. However, if the ball gets past the fenders, the goalie, whom Soper calls a “keeper,” is the last one standing between the opposing team and a disastrous goal. Soper calls some mental illness symptoms “keepers.”

Soper clarifies that his theory applies only to what are called “functional” mental illnesses, which are illnesses that cannot be traced to diagnosable bodily causes. These include “depression, generalized anxiety, substance use disorders (alcoholism and drug addictions), non-suicidal self-injury, PTSD, eating disorders, bipolar disorder, schizophrenia, obsessive/compulsive disorder (OCD), and other sundry ailments” (107). Organic mental illnesses, like Alzheimer’s and Down Syndrome, have clear bodily causes and thus count as true illnesses, and they are outside Soper’s purview. Similarly, Soper’s theory does not apply to developmental disorders like autism.

Some symptoms of these functional mental illnesses, or keepers, help us deal with both the pain and the brain side of suicidal motivation. Depression and substance use disorders like alcoholism help a person handle pain by numbing them to it. Non-suicidal self-injury, like cutting, which often occurs during mental illnesses, distracts people from their primary pain by providing a substitute. Delusions and psychoses distract a person from a painful reality by substituting another imagined one. Obsessions can also distract people from profound pain.

Mental illnesses also make planning and taking action more difficult, thus affecting the brain side of suicidal motivation as well. Suicide is facilitated by the ability to make a plan. Are you going to buy a gun or poison? Are you going to jump off a bridge at a certain time? Suicide also requires great resolve: one must stick to one’s terrifying plan. Mental illnesses render planning and resolve more difficult. Depressed people are listless and indecisive: they don’t want to do anything or think about anything seriously. An intoxicated alcoholic or drug user is similarly not in a state to think seriously about anything, especially if they have passed out, an effect of many drugs. Psychosis alienates us from reality entirely making the formulation of realistic plans difficult.

Thus, Soper conceives of some mental illness symptoms not as diseases, but as part of a kind of psychological immune system that evolved to cope with the temptation of suicide.

From his evolutionary theory, Soper derives important hypotheses about the nature of mental illnesses and how we should treat them. One fact about mental illnesses is that they are notoriously hard to define and distinguish from each other. Two people can be diagnosed as schizophrenic even if they share no symptoms. Comorbidity is another common aspect of a mental illness: about half of those diagnosed with a mental illness are also diagnosed with another illness. There are many depressed schizophrenics, psychotic depressives, and alcoholic bipolars.

Soper argues that that psychiatric diagnosis is so difficult because there is only one kind of keeper, which he calls “common mental disorder” (CMD). CMD consists of a suite of psychic tools, or symptoms, that deal with the pain and brain side of suicidal desire, like delusions, numbing, and listlessness. There is no difference in kind between psychiatric diagnoses like schizophrenia, depression, and OCD. Rather, these are different manifestations of the same basic suite of tools.

Most importantly, Soper believes that acceptance of his theory of mental illness would profoundly change the way that we treat the mentally ill.

If we changed our perspective towards mental illness, we could save lives and forestall misery. We could stop treating this kind of dis-ease as if it were a malevolent, incomprehensible monster. We could stop stigmatising those of us who are affected. We could stop making them out to be defective, deficient, or disordered. We could start to treat the human mind with the awe, humility, and respect it deserves. We could view depression, addictions, psychoses, and all the rest as aspects of the regular, healthy way by which the mind responds to the formidable challenge of being and staying alive. (129)

Soper believes therapists should treat the mentally ill with sympathy and support. He is skeptical about the value of psychiatric medication, which has not reduced the suicide rate. Rather, the best treatment for the mentally ill is to help them build lives worth living.

Though Soper’s theory is speculative, I am convinced that it must be part of the explanation of mental illness. The reason is that this theory fits the facts so well. Soper devotes a chapter of his book, The Evolution of Life Worth Living, to showing how his theory accounts for the facts of mental illness. The “pain-and-brain” theory explains why functional mental illness exists, why it takes the form that it does, why it is unique to humans, why it is rare before adolescence, and how it is connected to suicide and pain. Mental illness is a mysterious phenomenon, and Soper’s theory makes sense of it better than any other that I have encountered.

1. Virtually all the material for this article, including the quotations, comes from Soper, C. A. The Evolution of Life Worth Living: Why We Choose to Live. Self-published, 2021. Additionally, I consulted Soper’s The Evolution of Suicide. Cham, Switzerland: Springer, 2018. A number of academic articles by Soper are available online for free. A particularly useful one that contains clarifying graphs is Soper, C.A. Adaptation to the Suicidal Niche. Evolutionary Psychological Science 5, 454–471 (2019), available here. A recent summary of Soper’s theory is Soper, C.A. An Integrated General Theory of Psychopathology and Suicide. Evolutionary Psychological Science 9, 491–511 (2023), available here.