Kids With More Siblings Have Poorer Mental Health, Study Finds

The impact of having siblings has long been a topic of discussion. Now a new study looks at how it may affect mental health. The conclusion is that teens with more siblings have poorer mental health, according to research recently published in the Journal of Family Issues.

The study looked at 9,400 eighth graders in China and 9,100 eighth graders in America. In both countries, researchers asked children their responses to a variety of statements to assess their mental health. In America, those included how they felt about statements such as, "I feel good about myself," "Every time I try to get ahead, something or somebody stops me," and "I certainly feel useless at times," among others.

"The most important finding is that the number of siblings is inversely associated with mental health in both countries," says Douglas B. Downey, PhD, a professor, and director of undergraduate studies in the sociology department at The Ohio State University, who conducted the study with Rui Cao, a doctoral student at the university.

Teens with no siblings in China were found to have the best mental health, while teens with no or one sibling fared best in America. On the flip side, in the U.S., those with older siblings or siblings close in age, particularly those born within a year of each other, were most impacted.

Dr. Downey points to two main possibilities for the findings. "Siblings dilute parental resources and compromise the quality of family interactions, leading to lower mental health, or the effect is not causal; the kinds of families that have many versus few children are different in the first place and less conducive to strong mental health," he explains.

For Dr. Downey, the results are important to look at during a time when people are choosing to have fewer children. The average household size in America has been shrinking for decades. It's a trend that's been taking place worldwide.

"Most countries are moving toward lower fertility—that means more children will be raised with fewer or no siblings," explains Dr. Downey. "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."

Digging Deeper Into Siblings and Mental Health

It's important to note the quality of siblings was not studied. "Previous research suggests that quality of sibling relationships matters—no surprise," says Dr. Downey. "If we could have measured quality we probably would have found that additional siblings—ones where sibling relationships are healthy—are probably good for mental health."

That's true: previous research has documented several pros of having siblings, which the study authors also point out. Healthy sibling relationships can lead to empathy and academic achievement, and be a much-needed support system.

"Sibling relationships can be great training grounds for practicing important social skills like conflict resolution, and adult siblings can give each other support in adulthood," says Emily Edlynn, PhD, clinical psychologist, Parents medical reviewer, and author of Autonomy-Supportive Parenting: Reduce Parental Burnout and Raise Competent, Confident Children, who was not part of the study.

Families with only one child have perks too, including kids not having to compete for attention. "Sometimes, parents may be less stressed with one child compared to multiple, but there can be a burden of feeling like the child depends only on the parent to be busy and entertained," adds Dr. Edlynn.

Family circumstances can also impact children's feelings. "In my therapy practice, I have seen the dynamic of one child having significant medical or psychiatric needs that require a lot of attention from parents," says Dr. Edlynn. "Siblings of these children often need extra support for coping with how one child's high-level needs may affect the whole family."

Some kids bully younger siblings, putting them at risk for mental health issues. There are also situations where caregivers already under high stress just have it "exacerbated by attending to the needs of multiple children," Dr. Edlynn points out.

But if you're a parent with multiple kids, don't despair. There are ways to ensure you are supporting each of them.

"As a mother of three myself, I know it's possible to be an attentive and responsive caregiver to more than one or two children," says Dr. Edlynn. "Just remember to see each relationship as unique and special, and tune into what kind of attention each child wants (e.g., deep talks or a fun outing). Do your best to carve out one-on-one time regularly, even if it's just a few minutes before bed."

No matter where your family falls or what your future plans are, Dr. Edlynn also stresses, "The general trend in the research has been there's no significant difference overall between only children and kids with siblings, though, so I think it's really about family preference for what works best for them."