Only children in the UK are doing just fine

Picture credit: Susan Jane Golding

12 July 2022

By Jenny Chanfreau and Alice Goisis

One-child families are becoming more common in many countries, including the UK. According to the Office for National Statistics, 18% of women born in the early 1970s had one child only, up from 12% among women born a decade earlier in the early 1960s and 14% among women born about a generation earlier, around 1945. Yet many outdated preconceptions and stereotypes persist about what only children are like and how their lives turn out. Our project, using data from four British birth cohorts born in 1946, 1958, 1970 and 2000-2002, provided a comprehensive analysis of the characteristics of only children born in different decades in the UK and how they are doing in childhood and adulthood. Overall, the picture that emerges around only children in the UK is reassuring.

For any research on only children, we first need to be clear about who is an only child. This might appear straight-forward at first glance, as the dictionary definitions of ‘Only child’ suggest: a child who has no sisters or brothers (Cambridge); a person who has no siblings (Collins); or a person who never had a brother or sister (Merriam-Webster). Yet closer reflection reveals added complexity. Are we talking about siblings sharing both parents or either? Or is it the experience of growing up without other children in the home – including social (i.e. step, adoptive or foster) siblings? If so, what about social and half siblings growing up in another household?

The lived experience of being an only child or a sibling may differ across households but also at different stages in life. A large age gap, or never co-residing, may mean an individual effectively grows up experiencing an ‘only child’ childhood but in adulthood the relevance of having a shared parent may come to the fore in matters relating to caring for ageing parents or inheritance. How you define ‘only children’ can affect the conclusions about the outcomes and circumstances of the group, but clearly the definition depends on what information is available in the data. In our project, we focused as far as possible on not living with other children in childhood and defined only children as those without co-resident biological or social siblings at age 10-11. The percentage of only children fluctuated from 14% in the 1946 study, down to 7% among those born in 1958 and back up to 9% in the latest cohort.

We began by looking at only children’s cognitive outcomes measured at around age 10-11 in each of the studies. We showed that only children have similar scores to children from two-child families and higher scores than children growing up with two or more siblings. However, the only child ‘advantage’, despite being consistently positive, appeared to be weaker in the most recent cohort compared to the earlier ones. We interpret this trend over time as showing that being an only child – despite on average being correlated with growing up in relatively advantaged families in the UK – has over time become relatively more associated with potentially disadvantaged circumstances such as parental separation. This work has highlighted that the diverse characteristics of one-child families are critical for understanding the well-being of only children and that being an only child is not a constant entity but is conditional to changes in societies.

Next, we looked beyond the childhood stage, finding that only children are more likely than those with siblings to provide care in middle adulthood for ageing parents. However, contrary to what we might expect, their well-being is not worse affected for being their parent’s only child available for caregiving. Our project has also investigated physical health. Existing research from different countries had suggested that only children may be at risk of poorer health, in particular more likely to have BMI classified as overweight or obese. We investigated how BMI develops  throughout childhood and across adulthood for individuals born in different decades. Like research from other contexts, we also found that in each of the cohorts only children have slightly higher BMI on average during school age. Importantly, however, we also found that this difference in childhood is very small and that the BMI trajectories converge, so among adults only children and siblings have similar levels of BMI. Because high BMI is not itself an adverse health outcome, but rather an indicator of elevated risk of later ill-health, these findings raise doubts about whether the difference in BMI should be of concern in the UK context.

For the next stage we are therefore turning to investigate only children’s health in middle age directly, and our preliminary findings suggest that in the UK the health of only children in their 40s, 50s and early 60s may not differ from people with siblings. Unlike the outdated preconceptions and stereotypes about only children, the findings from our project thus suggest an overall reassuring picture of UK only children’s lives and outcomes.

Photo by Susan Jane Golding via Creative Commons