Banner by Katherine Greener and Devika Diwan

Why do We Still Suffer from Mental Illness? 

by Nicholas Rosa

While proper mental health diagnosis is a relatively new concept, mental illnesses and the genes behind them have been circulating through our evolutionary pool since the first humans. A basic understanding of evolution shows that genes beneficial to a species’ survival are kept via natural selection, while unfavorable genes get filtered out. Despite this regulation, hundreds of millions of people suffer from mental illnesses, causing significant strain on their normal, day-to-day functions. If mental illnesses are both genetic and inherently harmful, why haven’t they been filtered out of the gene pool? Recent studies have shown that mental illnesses such as generalized anxiety disorder, obsessive compulsive disorder, bipolar disorder, ADHD, and schizophrenia (among others) have either evolutionary or biological traits keeping them alive.

Generalized anxiety, or GAD, is a common mental illness known to cause the suffering of many, making even common tasks seem insurmountable. GAD is defined by the National Institute of Mental Health as “characterized by excessive anxiety and worry about a variety of events or activities that occurs more days than not, for at least 6 months”. Unlike common anxiety, someone with GAD has persistent anxiety, even when one knows what they’re worrying about is irrational. Some scientists point to the concept of ancestral neutrality as a means for explaining why such a damaging illness can be so prevalent in our gene pool. Ancestral neutrality theorizes that some genetic traits considered negative today could have been evolutionarily beneficial (or benign) to our ancestors. Ancestral neutrality is commonly shown in many of our unnecessary physical traits (eg. the appendix) or biological drives (eg. obesity as a result of innate desires for fatty foods), but can also be shown in many mental illnesses people suffer from today.  Dr. John S. Price of the Department of Psychology at the  Brighton General Hospital elaborates on this in his paper Evolutionary Aspects of Anxiety Disorders. Price defines anxiety as something brought on by what we would consider “bad news”. Prices points out the drastic quantitative difference of bad news exposure between us and our ancestors. Hunter gatherers in small bands of people did not have the constant bombardment of news, social media, and the intricate system that civilization has given us. Price also argues that the bad news of our ancestors was discussed and solved amongst the community as a whole, whereas we tend to experience bad news by ourselves. GAD, however, is not the only mental illness that can be attributed to ancestral neutrality. Obsessive compulsive disorder, or OCD, can also be attributed to this concept.  The National Institute of Mental Health defines OCD as “a common, chronic, and long-lasting disorder in which a person has uncontrollable, recurring thoughts (obsessions) and behaviors (compulsions) that he or she feels the urge to repeat over and over”. OCD can have take a significant mental toll on those afflicted, and can make simple tasks seem torturous. In their paper, An Evolutionary Hypothesis For Obsessive Compulsive Disorder: A Psychological Immune System?, Consultant psychiatrists Dr. Riadh Abed and Dr. Karel de Pauw argue that OCD differs evolutionarily from other anxiety disorders as anxiety disorders prevent us from exposure to immediate “bad news”, whereas OCD prevents us from ever experiencing “bad news” in the first place. Abed and de Pauw suggest that OCD is the cause of an an overactive mental model, used to think about potential dangers in the world, thus knowing how to respond if they ever do present themselves. While our ancestors may have benefitted from this overactive mental model, allowing them to be prepared for any threat in the unknown world they inhabited, the negative effects of OCD in today’s times are quite visible. In such a contemporary and emotionally complex civilization, OCD can lead to arbitrary and damaging repetitive thoughts and habits.

While all signs point to anxiety disorders and OCD having their roots in evolution, other debilitating disorders have their roots in biology. Bipolar disorder, schizophrenia, ADHD, and autism all have considerable negative effects on those afflicted. Bipolar disorder — a brain disorder causing arbitrary and sudden changes in mood and ability to interact in normal societal settings — and schizophrenia — a severe mental disorder affecting a person’s control over their perception of reality — harm millions, sometimes leaving them completely unable to function normally. It would be irrational to consider these severe mental disorders as having any benefit in our ancestors. Such disorders are kept in our gene pool through biological factors, like rare deleterious mutations. Dr. Naomi Wray of the University of Queensland in Brisbane, Australia, conducted a study tracing depression, bipolar disorder, ADHD, schizophrenia, and autism, to the same genetic variations. This study shows how important genetic variants are to the mental health world, as these five mental illnesses account for 17-28% of all diagnosable mental health problems. A study performed by Dr. Aliz Rao et al. at UCLA, titled Rare deleterious mutations are associated with disease in bipolar disorder families, discovered that deleterious genes play a heavy role in the passing down of bipolar disorder.  Deleterious genes are genes that exhibit traits primarily and directly damaging to the person’s chance of survival and/or carrying out a normal life. These genes can be carried in the recessive allele of a heterozygous person. If two people with the heterozygous version of a trait with a deleterious recessive allele have offspring, there is a 25% chance their offspring will have the deleterious trait, despite neither of the parents showing the trait themselves. This is crucial to our understanding of why mental illnesses stay in our gene pool, because those who have offspring afflicted with a mental illness do not necessarily have to have that mental illness themselves.

Even if we took it upon ourselves to filter out mental illnesses, our genetic makeup would ensure it would never truly be eradicated. It is great to know why we have mental illnesses, how the could have been beneficial in the past, and why they can’t necessarily go away through evolution, but that still leaves the great pain of mental illnesses themselves. While we cannot inherently get rid of these illnesses, we do live in a time where the benefits of cutting edge genetic studies can allow for early detection, proper diagnosis, and in turn successful treatment and management. These studies also further prove that mental illness is in fact a genetic issue, and is something beyond the person’s control. While we cannot end mental illness, we do have to power to end its stigma.