More Siblings Might Mean More Mental Health Struggles

The conventional wisdom when it comes to families has been the same for parties: the more the merrier. But now new research wants us to rethink that with its findings that seem to suggest that teenagers with siblings have poorer mental health.

The Journal of Family Issues published the report.

Research Without Borders

This groundbreaking study, spearheaded by professor Douglas B. Downey, Ph.D., a director of undergraduate studies in the sociology department at The Ohio State University, and Rui Cao, an OSU doctoral student, looked at 9,400 Chinese eighth graders and 9,100 U.S. eighth graders.

The researchers questioned the children in each country to gauge their mental health. Because of China’s decades-long Once Child Policy, which the government ended in 2016, the average child there boasts fewer siblings than his average American counterpart – .89 compared to 1.6.

A Surprising Sibling Association

“Our results couldn’t have been easily predicted before we did the study. Other studies have shown that having more siblings is associated with some positive effects, so our results were not a given,” Downey explained. “The most important finding is that the number of siblings is inversely associated with mental health in both countries.”

In short, Downey’s research showed that Chinese teens without siblings had the best mental health – according to his metrics while U.S. teens with no or one sibling boasted better mental health.

Conversely, U.S. teens with older siblings or with siblings close to the same age suffered the most.

But Why?

Downey and Cao proposed a pair of theories to explain the dichotomy by suggesting that either:

1. Parenting might be a zero-sum game. “Siblings dilute parental resources and compromise the quality of family interactions, leading to lower mental health,” Downey offered.
2. Or the effect is not causal. And “the kinds of families that have many versus few children are different in the first place and less conducive to strong mental health,” he added. The research results also seem to support that since socioeconomic advantages translated to better mental health outcomes in both countries.

The findings emerge when many nations are suffering a drop in birth rates. For example, birth rates have been falling in the United States since 2009. That year, there were 13.5 births for every 1,000 U.S. residents. By 2020, that number had fallen to 10.97. That represents a 23 percent drop.

It’s also worth noting that births nudged northward in 2022 to 11. But it’s too early to tell if that marks a sustainable rebound or a statistical anomaly.

“Most countries are moving toward lower fertility — that means more children will be raised with fewer or no siblings,” Dr. Downey observed. “We don’t fully understand the significance of this demographic change, but our study finds an association — more siblings are associated with lower mental health — that may be one of the consequences.”

Sibling Questions Remain

Finally, the researchers pointed out that the data doesn’t address the question of the quality of those sibling relationships. Downey suggested that better sibling relationships would positively influence teens’ mental health outcomes.

In fact, multiple studies over the years have suggested that sibling relationships tend to support better mental health, whether it’s reduced odds of divorce later in life or better social skills.

“This combination of results is not easily explained. We still have more to learn about the impact of siblings,” Downey said.

Further Reading:

Vaccination Among Children With Developmental Delay and Their Siblings

Controversial Issues in Child Psychiatry

Treatment and Outcomes in Adolescents With Schizophrenia