Overdoses of the oxytocin can occur occasionally, and I’m not talking about the ultra rare case of a physician injecting too much of the hormone to induce labor or abortion, or to control bleeding following delivery. There is a genetic disorder that shows up with a person acting, well, too friendly –too excited to encounter both familiar people and strangers, often to the point of wanting to embrace them in situations when doing so is way beyond the societal norm. The disorder is called Williams syndrome and it’s the topic of a new book, The Boy Who Loved Too Much, reviewed recently in the New York Times.
Oxytocin has been a topic of discussion here on The Pulse. It’s a hormone that is produced in the hypothalamus region of the brain and then secreted from the pituitary gland into the blood, which transports it throughout the body to produce various effects. The most famous effects of oxytocin are stimulation of contraction of the uterus and ejection of milk from the breasts, but the hormone plays many other roles. Acting on the kidneys, for instance, oxytocin influences the amount of water excreted in urine and the concentration of sodium in blood. Some research suggests a role for oxytocin in appetite among other things, but the hormone is also being recognized increasingly for various roles in behavior and emotion.
In particular, there is a connection between human bonding and oxytocin. The relation is probably very complex, but one dimension involves how much need a person feels to interact with others. You may have heard that oxytocin is thought to be a major player in promoting bonding of the mother with a nursing infant. The trigger in this case is sucking on the nipple, but the connection is not as straightforward for human interactions that are more complex.
In autism spectrum disorder (ASD) for instance, absence of the gene encoding a cell receptor that normally binds oxytocin, enabling it to work as a neurotransmitter (a chemical messenger between nerve cells), has been implicated in the avoidance of physical and emotional contact with other people. If this is true, it means that the brain in ASD is not responding to oxytocin, which supports the idea that oxytocin is an important factor promoting bonding and love.
Williams syndrome results from a random deletion of 26 genes, resulting in emotional but also physical effects. It is inherited with autosomal dominant genetics, meaning that boys and girls are affected equally and that one parent with the condition is enough for a child to be affected. The syndrome features a heart defect called supravalvular aortic stenosis, which may have to do with the absence of a gene that makes body tissues stretchy. It also features problems in the digestive tract, plus the syndrome is associated with hypercalcemia (high levels of calcium in the blood), leading to hypercalciuria (high calcium in the urine), leading to a high risk for kidney stones. Because of the heart disease, people with Wiliams syndrome have reduced life-expectancy compared with the population as a whole.
On the emotional dimension though, affected people have a kind of pathologic friendliness that makes it a kind of polar opposite of ASD. One interesting tidbit covered in the new book is how particular facial features of Williams syndrome –a short nose, broad forehead, and full cheeks– gives the person an “elfin” appearance. Thus, it has been suggested that presence of people with Williams syndrome in times past could have been the basis for stories about elves, fairies, leprechauns, and similar smiley mythological beings.
That’s how they appear on the outside, but it also seems to be the case within the brain. In contrast with the poor response to oxytocin in ASD, people with Williams syndrome typically have three times the usual level of oxytocin in their blood, and it stays elevated all the time. This is in contrast with normal individuals, whose oxytocin level spikes up at particular moments.
The lack of the 26 genes also underlies mental disability in Williams syndrome. Mean intelligence quotient (IQ) score in this condition is just below 70 (the IQ mean of the general population is just above 100, with more than 2/3 scoring 85-115). But their performance is often much better in certain areas than what such a low IQ would predict. Typically, they have very low with spatial-geometric capability (a major component of IQ testing). This relates to a problem with depth perception, which in some cases can lead a person with Williams syndrome to avoid escalators. But they tend to have good verbal skills –often above normal– and musical ability far in excess of what should be expected for the IQ.
Even more rare than the typical Williams syndrome is a form of the syndrome that researchers have discovered in certain young woman. Like others with Williams syndrome, she suffers from various physical afflictions connected with the usual 26 missing genes. But she does not display the pathological friendliness trait. She relates normally to other people, and, rather than missing all 26 genes, she was found to have a normal copy of a gene involved in how the body handles oxytocin. This case supports the idea that the extreme friendliness in Williams syndrome may depend on just one gene.
How does society react to the condition? Commonly, people are put off by the extreme need for physical contact and conversation that characterizes Williams syndrome. It seems that autism and Williams syndrome represent opposite extremes of a friendliness curve, which raises the question of why we would evolve to favor a happy medium, a Goldilocks zone of friendliness. Wouldn’t it be better if we humans simply acted as friendly as they possibly could to the point that everyone is hugging strangers constantly? But from an evolutionary standpoint, the answer seems very clear. In prehistoric times, the tendency to hug everyone that you meet probably would have had terrible consequences for your chances of survival. You might be worried about any stranger as a potential attacker, or the huggee might see a hug from a stranger as an attack and react violently. On the other hand, having the ability to adjust one’s feeling of closeness to others due to changes in the level of hormone would be an enormous advantage.