Teenagers’ mental health suffers when they have more siblings

COLUMBUS, Ohio — The more children that families have, the worse kids’ mental health gets. An alarming new study has found that teenagers from larger families tend to have poorer mental health compared to those with fewer siblings.

It’s a surprising discovery that spans across two vastly different countries: the United States and China. This research, conducted by sociologists from The Ohio State University (OSU), delved into the complex relationship between sibling count and mental well-being.

“Our results couldn’t have been easily predicted before we did the study,” says study lead author Doug Downey, professor of sociology at OSU, in a university release. “Other studies have shown that having more siblings is associated with some positive effects, so our results were not a given.”

Their research involved extensive analysis of over 9,400 Chinese and 9,100 American 8th-graders. The average Chinese youth has about 0.7 fewer siblings than their American counterparts, likely influenced by China’s One Child Policy.

The study’s methodology included asking students (average age of 14) various questions about their mental health. These questions, though different in each country, led to some intriguing insights. For instance, in China, teens without siblings showed the best mental health, while in the U.S., those with none or one sibling fared similarly well. However, the presence of half and full siblings displayed a link to poorer mental health in the U.S., especially when siblings were close in age or older. One explanation for these findings is the “resource dilution” theory.

“If you think of parental resources like a pie, one child means that they get all the pie — all the attention and resources of the parents,” notes Downey. “But when you add more siblings, each child gets fewer resources and attention from the parents, and that may have an impact on their mental health.”

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This theory is reinforced by the negative impact observed in families with closely spaced siblings, who compete for similar parental resources.

Another aspect considered is the “selectivity explanation,” which suggests that families with many children may differ in ways that could affect their children’s mental health. For example, in both China and the U.S., children from socioeconomically advantaged families exhibited better mental health. This was most noticeable in one-child families in China and in children with zero or one sibling in the U.S.

“What we found is that when you add all the evidence up, the effect of siblings on mental health is more on the negative side than the positive side,” says Downey.


While these findings predominantly highlight the negative impacts of having more siblings, Downey notes that sibling quality wasn’t a factor in this study. High-quality sibling relationships could potentially offer positive effects on mental health. Moreover, other research finds that having more siblings can improve social skills in young children and decrease the likelihood of divorce in adults.

Downey concludes by acknowledging the complexity and significance of these results, especially as countries like the U.S. experience lower fertility rates.

“Understanding the consequences of growing up with fewer or no brothers and sisters is an increasingly important social issue,” says Downey.

The study is published in the Journal of Family Issues.

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About the Author

Matt Higgins

Matt Higgins worked in national and local news for 15 years. He started out as an overnight production assistant at Fox News Radio in 2007 and ended in 2021 as the Digital Managing Editor at CBS Philadelphia. Following his news career, he spent one year in the automotive industry as a Digital Platforms Content Specialist contractor with Subaru of America and is currently a freelance writer and editor for StudyFinds. Matt believes in facts, science and Philadelphia sports teams crushing his soul.

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