Growing up in cities is linked to earlier puberty in girls, according to a new groundbreaking study by Chinese researchers that also found lasting differences in adult brain structure and personality.

The findings were published in “Nature Cities,” a subsidiary of the science journal Nature, on Dec. 15 by a team led by Yu Chunshui, Director of Radiology at Tianjin Medical University. Their research examined how childhood urban environments may shape biological and neurological development later in life. 

Researchers analyzed data from 2,950 healthy young Han Chinese women raised in urban and rural settings, drawing from the Chinese Imaging Genetics Cohort (CHIMGEN) — a large-scale project examining how genetic and environmental factors interact to shape brain structure and behavior.

To assess the timing of puberty, the researchers used the age at which participants reported their first menstruation as a biological marker. Childhood exposure to urban environments was measured using indicators such as the extent of built-up land and nighttime light intensity from birth through adolescence.

The study also used MRI scans to analyze brain volumes and personality assessments to examine individual traits. The results showed that higher levels of childhood urbanization and earlier puberty were both associated with reduced volume in parts of the medial prefrontal cortex. 

Participants exposed to more urbanized childhood environments also scored lower on measures of agreeableness, sensitivity to social approval and emotional responsiveness, the study found.

Both family-level and city-level socioeconomic status influenced the timing of puberty, according to the results of the study, creating a more nuanced picture of the impact of urban environments on biological and neurological development.

The findings suggest that urban pressures in childhood may biologically encode a more self-reliant orientation in young urban women. Researchers also underscored that similar neurobehavioral patterns have been historically associated with higher vulnerability to mental health disorders, including major depressive disorder and schizophrenia.

The researchers framed their findings in terms of “life history theory,” which holds that organisms adapt their development to perceived environmental risk and stability. From this perspective, cities — despite their material abundance — may be interpreted biologically as high-stress, high-competition environments. The resulting adaptation is earlier puberty and the body prioritizing reproduction over neurological development.

The authors cautioned that further research is needed, particularly involving male participants, to determine whether similar mechanisms operate across genders and how different urban conditions may shape development.

Editor: Marianne Gunnarsson.

(Header image: Ma Jian/VCG)