Distinguishing disorder from healthy states – Evolutionary Ecology of Health Research Labs

The predominant view within medicine and psychiatry considers a trait to be a disorder if it causes pain and suffering, or if it impairs functioning in some important domain of life. However, an evolutionary perspective suggests that pain mechanisms are adaptations that play an important role in maintaining health by drawing attention to problems that threaten growth, survival, maintenance, or reproduction. People born with an inability to feel pain tend to die at an early age because they are more likely to get injured and less able to take care of injuries, or the source of the pain.

Pain mechanisms represent a class of trait that evolved to respond to the stressors that interfere with growth, survival, maintenance or reproduction. Adaptive responses to stress often require the allocation of limited resources, such as energy or attention. For instance, when you get sick with an infection, your body up-regulates the amount of energy devoted to your immune system, while it down-regulates other systems in your body that could draw limited energy resources away from fighting the infection. The impairments that occur while you are sick (e.g., lethargy and sleepiness, difficulty thinking, reduced physical activity) therefore represent an adaptive trade-off that the body makes in how it allocates energy to respond to the threat of infection.

Analogously, some psychological traits that are currently considered mental disorders because of the impairments they cause could alternatively be adaptations that evolved to respond to important stressors. One example of these psychological states is depression: much of the current research in the Evo-Health Lab focuses on understanding the cognitive ecology of depressed mood (i.e., how the cognitive effects of depressed mood relate to the problems that triggered the mood state). Depressed mood does not have the features of a disorder. For instance, it promotes an analytical processing style in which a complex problem is broken into smaller, more manageable components, and then the components are studied in turn. Click here to learn more about the Cognitive Ecology of Mood project.

We must be able to correctly distinguish disorder from healthy states in order to properly and effectively diagnose and treat individuals.

Many of the most commonly prescribed medications are used to suppress painful symptoms and reduce suffering. Since pain is often (but not always) an adaptive response to stress, the suppression of symptoms can have adverse effects on health. By improperly diagnosing and treating individuals, we put further risks on those who can benefit from alternative types of therapy. Our recent work in this area has focused on analyzing the health effects of antidepressants on the neurotransmitter systems that regulate depressive symptoms (particularly serotonin and norepinephrine), as well as the overall health effects of antidepressants on the functioning of the body. For example, recent studies have found that placebo drugs are nearly as effective as antidepressants themselves, accounting for about 80% of the antidepressant response. In fact, antidepressants have been associated with adverse and often harmful symptoms (such as cognitive impairment, digestive disorders and suicidal ideation). We have also begun to examine the health effects of antipyretic (fever-reducing) medications (click here to learn more about these studies).

Remove unnecessary stigma around many mental and physical conditions

Currently, diagnoses for many mental conditions are based on arbitrary criteria set by the Diagnostic and Statistical Manual of Mental Disorders (DSM for short), rather than on objective and scientific criteria. Often, criteria for many mental disorders are based on arbitrary social labels, stigmatizing unwanted social behaviour based on current social norms. For example, conditions that were labelled as clinical “disorders” in previous DSM editions include:

Homosexuality
Lack of vaginal orgasm

Many other questions arise when attempting to categorize mental states: Why are only negative statistical extremes (such as depression and anxiety) considered disorders (and not extreme generosity or kindness)? Who decides where the cut-off between normalcy and disorder lies? Are the conditions surrounding one’s mental condition, such as poverty or extreme conflict, always considered in every diagnosis?

As mentioned above, the misdiagnosing of individuals can often lead to dangerous and harmful consequences. By basing treatment on an arbitrary set of general diagnostic traits, patients may be exposed to unnecessary and sometimes harmful drug therapies. In a social context, the mislabelling of one’s mental state and behaviour can often lead to social ostracizing and bias.

Evolutionary research and analysis of mental processes and the actual instances of breakdown of these mechanisms will aid in understanding the valid discriminators between disorder and nondisorder by applying scientific reasoning rather than arbitrary criteria. By better understanding what constitutes a disorder, and what are merely socially unfavourable but beneficial adaptations, we will be able to more properly diagnose and treat individuals with reduced risk of improper therapy.