The size of the average family is getting smaller, with even the Duke and Duchess of Sussex claiming they’ll only have two children, “maximum”, for the sake of the planet. And according to new data from the Office for National Statistics, one-child families are becoming increasingly common. Just over 40 per cent of UK families have one child, and that figure is even higher among cohabiting and single parents. Over in America, the proportion of parents with only one child has jumped from 11 per cent in 1976 to 22 per cent in 2015.
Yet it’s fair to say that being an only child still has some stigma attached to it. There’s a pervasive myth that only children are selfish, demanding, and struggle with basic concepts like sharing, while those with siblings are thought to learn these social skills by default.
These ideas may well be traced back to 1896, when the respected child psychologist Granville Stanley Hall declared “being an only child is a disease in itself.” While Hall was considered an excellent psychologist at the time, his science would be considered somewhat questionable today. For example, his study involved surveying teachers and doctors about ‘unusual children’ and the responses he got back featured 46 only children out of 1,045 altogether.
So, how true are these stories? Can being an only child have physical or emotional health implications?
This week, a study in the Journal of Nutrition Education And Behaviour found that only children are more likely to be obese than families with multiple children.
The researchers studied food diaries kept by 62 American mothers to look at the eating habits of families, covering two weekdays and one weekend day, with teachers logging what the children ate at school.
The study found that families with multiple children tended to spend more time planning family meals and less time eating out, both of which helped to keep them trim. In total, 37 per cent of the only children were obese, compared to 5 per cent of those with siblings.
Admittedly this is a reasonably small sample size of a study and the results seem more to do with the economic realities of rearing multiple children than any specific developmental issues with regards to only children.
However, this is far from the only study which has looked into the health implications of being an only child. There’s a particular interest in this field of study in China, where from 1979 until 2015, a single-child policy was in effect across the country.
One study conducted by scientists at the University Of Beijing in 2016 found that only children had a slightly different brain structure compared to siblings, specifically with regards to the volume of grey matter.
The study didn’t demonstrate any difference in intelligence between only children and those with siblings, but it did show that only children perform better in tests of flexibility (a measure of creativity) and score lower in terms of agreeableness. Physically, only children’s brains showed greater supramarginal gyrus volumes, an area of the brain associated with language processing and a smaller medial prefrontal cortex, an area focused on emotional regulation and social behaviours.
However, another study (also from China) found that only children are statistically more likely to show high degrees of narcissism than those with siblings.
In the West however, much of the research on only children has been conducted by Toni Falbo, a professor of educational psychology at the University of Texas.
One of Falbo’s early reviews from 1979 found that only children are just as well-adjusted as those with siblings and that they do better in school, have more motivation, better self-esteem, and are more gifted socially. Another analysis of studies conducted by Falbo found that while first-born children and younger siblings from two-child families did better in terms of intelligence and achievement, only children performed better on these metrics than any other configuration of children and across all developmental outcomes, only children were indistinguishable from firstborns and people from small families.
A longitudinal study of 10-12-year-olds across Germany found that only children had better relationships with their parents. A quarter described their relationship with their parents as ‘good’ while under 24 per cent of firstborns, 20 per cent of middle-children, and 18 per cent of youngest siblings said the same. The researchers found this was because the only children could talk to their parents about important matters more easily.
However, some of the studies into only children can be contradictory.
For example, a study from the Ontario Mental Health Foundation found that only children are more likely to be submissive and have overprotective parents, while a study from Chiang Mai Medical School found that only children are more ambitious, confident, intelligent and independent.
Similarly, a large-scale study from the Gerontology Research Center, National Institute of Aging, National Institutes of Health in America, found that being an only child has absolutely no impact on personality or intelligence whatsoever.
So where does the real answer lie? Sibling researcher Aviden Milevsky once wrote he noticed that “often researchers who themselves are only children are the ones forwarding the findings in favour of only children and those with siblings propose that singletons are disadvantaged.” He suggests that there may be some bias at work in the science of the subject.
Overall, it seems that being an only child doesn’t have any health implications either way, but rather it’s to do with how that child is raised.