New Worlds: Intellectual Disability

To the modern, western, medical mind, intellectual disabilities are generally distinct from mental illnesses. But as we’ve already discussed, other frameworks for understanding such problems attribute them to different causes, and as such, don’t necessarily differentiate the one from the other. In particular, the responses to them were often the same, so before we turn to that aspect next week, let’s take a look at this corner of the topic.

Over the centuries, we’ve had a lot of words for people with intellectual disabilities, many of which (warning for what’s about to follow) are considered offensive now. Idiot, fool, simpleton, half-wit, cretin, dunce, moron, imbecile, retard . . . what’s interesting about them, at least to me, is how many were originally intended to be impartial medical descriptions, not insults. Retard, for example, which has a great deal of force as a slur nowadays, comes from the (now outdated) use of “mental retardation” as a scientific term to describe intellectual development that lags significantly behind the norm. “Cretin” may have gone even further than that; the predominant theory for its etymology is that it derives from the French chrétien or “Christian,” and was intended to remind people that these souls were fellow children of God. (It is not, as I saw one internet post suggest years ago, originally an ethnic slur against people from Crete.) Physicians during the eighteenth and nineteenth centuries poured a great deal of effort into creating hierarchies of disability, using different terms to classify people based on their degree of impairment, in a way that reads peculiarly at best nowadays.

A note before I continue: I’m going to be referencing two things in the following discussion — intellectual disabilities and behavioral problems — because it’s not uncommon for conditions that cause the one to also cause the other. I want to be clear up front, though, that this doesn’t mean everyone with an intellectual disability is also e.g. violent towards others. It depends very much on the specific condition and individual; Down syndrome, for example, rarely leads to violent behavior, while fetal alcohol syndrome even in milder (non-disabling) forms is strongly correlated with risky behavior and trouble with the law. So as with all of our topics this month, if you want to include them in your writing, handle with care, lest you perpetuate harmful stereotypes.

A great many intellectual disabilities are inborn, one way or another. Some are due to genetic causes; of those, a small percentage (perhaps one in twenty) are inherited, while others are the result of mutation on specific genes. Other cases are created during pregnancy or childbirth, for example if labor goes badly and causes the baby to be deprived of oxygen for a time. Some infections badly affect not only the mother but also the fetus, as with congenital rubella syndrome, which can produce a wide range of both physical and mental disabilities in the child.

We know that pregnant and breastfeeding women should not consume alcohol, lest their children develop fetal alcohol syndrome — but what about in the past, when alcohol was commonly consumed by everyone and was often safer than water? Turns out that our ancestors were aware of the problem, too, though they didn’t fully understand the mechanism, and often focused more on the dangers around conception than the whole of pregnancy. (I find it oddly charming that, because of that focus, they were also concerned about immoderate drinking in fathers.) The lack of full understanding and the ubiquity of drinks like weak beer, not to mention the time that elapses between conception and knowing you’re pregnant, mean that mild forms of FAS may have been hugely common throughout history — and I strongly suspect, though can in no way prove, that this contributed to the high rates of crime and violence we see in the past. But that “past” isn’t as far behind us as you might think: doctors in the 1960s and 1970s were still recommending alcohol, sometimes as an intravenous injection, to stop premature labor.

Other intellectual disabilities are acquired later, particularly during childhood. Speaking of things that were common in history: malnutrition must have hampered the development of countless people in the past, given how common famines were. Even now, this is something we struggle to address in the developing world and the poorer segments of industrialized societies, and its effects contribute to perpetuating those inequalities. From a developmental perspective, late pregnancy and the first few years of life are the most critical period, during which a lack of nutrition can cause lifelong problems. Nor is this just a matter of inadequate food overall; iodine deficiency is considered the single most preventable cause of intellectual disability in modern times. Historically, communities that got a lot of their food from the ocean tended to be fine — marine foods contain lot of iodine — but mountainous regions and those subject to a lot of flooding often had (and have) iodine-poor soil. Ever wonder why most table salt is iodized? It’s to make sure we get enough of that nutrient.

Childhood diseases like measles and whooping cough can also stunt intellectual development, which is part of why the anti-vaccine trend in recent years is so troubling. We have better treatments now for many of those illnesses, but it’s far safer never to contract them in the first place. And the major surge in lead production during the Industrial Revolution exposed huge numbers of people to lead poisoning, which — when it occurs during childhood — is a major contributor to intellectual and behavioral problems. The last hurrah of that particular threat was the use of leaded gasoline during the middle of the twentieth century, and there are some highly convincing studies suggesting that the reduction in environmental lead since then is one of the major drivers behind the decline in violent crime: we have fewer and fewer adults who suffered the effects of lead exposure in childhood, when they’re most vulnerable to long-term damage.

Of course, not all such disabilities are present from childhood onward. We’ve massively increased our understanding of the damage caused by brain injuries, though our ability to reverse that damage is still extremely limited. The same is true of dementia, especially Alzheimer’s disease. And I should note that the kind of intellectual disability I’ve been discussing here is distinct from learning disabilities (more commonly called “learning difficulties” in the UK) like dyslexia, dyscalculia, and dysgraphia: those don’t affect a person’s overall intelligence, but rather the acquisition and performance of particular skills. Though again, historical understandings often lumped all these things plus mental illness together, much to the detriment of those affected.

What kind of life a person with an intellectual disability experiences depends on their condition, its severity, and the degree of medical and social support they receive. Results can range all the way from “this person lives as a fully independent adult” to “they will need significant caregiver assistance their entire life” — under ideal conditions. But unfortunately, conditions have often been, and still often are, far from ideal . . . which is what we’ll be discussing next week.