As families continue to get smaller worldwide, more children are growing up without siblings. This shift has raised important questions about how such early life experiences affect people later in life. Researchers are now focusing on how growing up without siblings might shape the brain, personality, and behavior of adults.
To address this gap, a team of researchers from Tianjin Medical University General Hospital and other institutions in China conducted a large-scale study to examine how growing up as an only child influences brain function and behavioral traits in adulthood. Their findings, published in Nature Human Behaviour, challenge many common assumptions.
Using data from the Chinese Imaging Genetics (CHIMGEN) study, which involved 32 research centers across the country, the researchers studied nearly 2,400 adults.
The participants were split into two groups: those who grew up without siblings and those who had at least one. To ensure a fair comparison, each pair was carefully matched based on similar demographic backgrounds, such as age, education, and socioeconomic status.
The study focused on analyzing brain structure, brain activity, mental health, cognitive performance, and personality traits. Researchers found several consistent patterns in adults who grew up as only children.
These individuals showed stronger connectivity in brain areas related to language, but weaker connections in regions responsible for motor control. They also had a larger cerebellum and a smaller overall brain volume, along with reduced spontaneous activity in the front and side parts of the brain.
In contrast to the stereotype that only children are more prone to behavioral issues, the study revealed more positive outcomes. Adults without siblings tended to score better in mental health assessments and showed stronger cognitive abilities. These findings suggest that being an only child does not inherently lead to negative outcomes.
The study also found that many of the observed brain and behavioral differences were closely linked to early life environments. Factors such as family income, the quality of maternal care, and emotional support played a major role.
The researchers concluded that while growing up without siblings can directly influence development, environmental conditions have a stronger impact.
These results point to the importance of early interventions, particularly for only children, to ensure they have access to enriching experiences and strong emotional support.
The study adds new depth to the understanding of how childhood experiences, especially in single-child households, can shape adult lives. As the number of one-child families continues to rise globally, the findings offer valuable insight into how supportive environments can promote healthy development.
