Can having siblings be harmful to your health? Here’s what studies show.

Your siblings can affect your physical and mental health more than you might imagine. A recent study published in the Journal of Family Issues analyzed the relationship between family size and siblings’ mental health in the U.S. and China and found that teens from larger families have poorer mental health than those with fewer siblings. The study raises questions about why having siblings might take a mental health toll on some and what are other ways that having a sibling influences your well-being. Obviously, every family is different, which makes this a very nuanced topic. Yahoo Life reached out to experts and looked at studies to uncover some possible explanations.

Here are some of the most likely reasons why having siblings might negatively impact your health:

Limited resources

It’s simple math: The more people there are to care for — assuming resources and parental capacity remain the same — the more that resources are divided up, leaving less to go around. Researchers call this phenomenon “resource dilution,” and the resources can come in the form of time, money, energy, attention and more.

“When children are raised in households with lots of siblings, sometimes the emotional needs of individual children might go unaddressed and unnoticed, leading some children to feel neglected, isolated, unseen and unheard,” Jennifer Nurick, psychotherapist and host of the Psychotherapy Central podcast, tells Yahoo Life.

Resource dilution can also be more literal, affecting finances and food on the table. “When there are more mouths to feed, there is obviously increased economic strain, which could lead to increased stress in the home environment that might affect the mental health of the whole family,” Nurick says. For example, a longitudinal study published in the Journal of Economic Psychology showed that financial strain in families is a significant predictor of mental health problems in children. “The study highlighted that children in economically strained households are at a higher risk of developing psychological issues, including anxiety and depression,” she explains.

This spreading-thin of supplies can also stress out parents, Nurick says, which can feed into the lack of emotional and personal resources for kids. “Parental stress can affect the overall emotional climate of the home,” she adds.

More research is warranted to explore the exact ways in which family size and resource dilution affect children’s and teens’ mental health, but there is significant evidence to support that a higher number of siblings and greater closeness in age can have a negative effect on younger siblings’ educational progress, specifically.

Competition

Those limited resources can also create competition. “Siblings may compete for parental attention,” Jeff Yoo, a therapist at the Moment of Clarity mental health treatment center, tells Yahoo Life. Nurick agrees, adding: “When more children are in the home, there is obviously more competition for parental affection, attention and resources. Depending on the parents and the family environment, this can result in rivalry, jealousy and comparison, which could potentially lead to anxiety and depression.”

Stressful home environment

“Living in a home with lots of different personalities and individual behaviors can lead to a more chaotic home environment with lots of noise, less privacy and more conflict,” says Nurick. “Some children might find this a stressful environment and find their nervous system is constantly in fight or flight, which could lead to various mental health issues.”

Older siblings caring for younger ones

“In large families, older children will often end up helping to care for younger siblings,” explains Nurick. “This can lead to children taking on the role of parents, known as parentification, and can cause stress and resentment and the loss of freedom for the older children taking on adult responsibilities,” she says. “This often occurs when the parents are out working a lot or choose not to be at home.”

Not only does this have a negative impact on older-siblings-turned-caregivers, it can damage younger kids, too. “I have seen younger children in this situation be bullied and mistreated by their older siblings, who are not mature enough to be taking on this role, resulting in varied mental health and self-esteem issues for the younger siblings,” says Nurick.

Yoo also makes a good point: For older siblings in this situation, “There is less time to develop as a child and more investment in being a worker in the family and picking up the slack,” he says. Alfred Adler’s birth order theory supports this. Though the theory is not perfect, it says that the order in which siblings are born affects life outcomes. One older study tested it on Latin American youth, focusing on substance use as a life outcome, and found that younger siblings were more likely to use substances than older ones, possibly due to the older siblings’ sense of authority and responsibility.

But having a sibling isn’t all bad news. There are plenty of well-understood benefits to having them.

Here are some examples of how siblings can improve your health:

Better interpersonal skills

A major positive impact of having siblings is its impact on developing social and interpersonal skills, points out Nurick. A study published in the Journal of Marriage and Family found that children with siblings, particularly those with a closer age gap, show higher levels of social skills than only children. “The research suggests that sibling interactions provide a unique context for developing social abilities, including negotiation, empathy and cooperation,” Nurick says, which are “things we know lead to an increase in the quality of relationships and mental health outcomes.”

More emotional support

Having siblings can be like having built-in playmates, partners, friends and companions for life. “They share a unique bond, having grown up in the same family environment, allowing them to understand and support each other in ways others may not,” Nurick says. “This emotional backing can be particularly beneficial during times of stress or change, such as moving to a new place, parental divorce or losing a loved one.”

All of these may also help to reduce feelings of loneliness and isolation, Yoo adds. Jenna Hermans, author of Chaos to Calm: 5 Ways Busy Parents Can Break Free from Overwhelm, tells Yahoo Life: “Even if they don’t ‘like’ each other, they can call on each other when needed for emotional support and feelings of belonging and connection. Because they share a family history and culture, siblings can also help individuals understand where they come from and who they are, establishing and confirming a sense of heritage and belonging.”

Greater resilience

“The challenges and conflicts that often come with sibling relationships can teach individuals how to cope with difficulties, bounce back from setbacks and persist in the face of adversity,” says Nurick. “These experiences can help build a foundation of resilience that benefits individuals throughout their lives.”

Yoo points out that “larger families often have more diverse personalities, interests and interactions. Siblings learn to share, cooperate and build strong bonds.”

Better physical health

Having siblings has been linked to better physical health, “which is closely linked to mental health,” Nurick notes. One study found that having older siblings speeds up the rate at which babies develop their gut microbiome, which may increase immunity and protect against food allergy sensitivities. Nurick says siblings often engage in more physical activity together, which could also lead to better health.

So do the pros outweigh the cons?

“It depends on the siblings you get,” jokes Nurick. She points out that, beyond considering the number of siblings, “an important factor is the quality of the sibling relationships.” Yoo agrees, adding: “It has everything to do with personal values, circumstances and priorities. Each family needs to focus on what aligns best with their goals and capacity.”