A major study drawing on data from the UK Biobank has found that childhood weight can shape the risk of depression and anxiety later in life, but reaching a normal weight in adulthood may erase much of that vulnerability. The research, published in the Journal of Affective Disorders, was led by Dong-Run Li, Ke-Ru Li and Bang-Quan Liu with corresponding author Qi-Jun Wu, all of China Medical University.
The researchers analysed a vast cohort of 368,756 adults aged between 40 and 69 at recruitment, who had no prior depression or anxiety diagnoses when the study began. They tracked medical records and self-reported health data for a median of just over 13 years to identify new cases of mental health conditions.
The study notes that mental health disorders and obesity are two of the world’s most pressing health challenges, with inflammatory processes and social factors linked to body fat potentially influencing mood and stress responses. It also emphasises the role of stigma and body dissatisfaction in shaping overall well-being for people living with obesity.
As for childhood weight, the findings indicate that any deviation from average size at age 10 was associated with higher risks of later mental health issues. Participants who recalled being thinner than average had about a 9 percent higher risk of depression and a 13 percent higher risk of anxiety, while those who remembered being plumper faced a 19 percent increased risk of depression and an 11 percent increased risk of anxiety.
Adult weight showed an even stronger link to mental health, following a U‑shaped pattern. The lowest depression risk occurred at a body mass index of roughly 23 to 24, within the normal weight range. Beyond that, the risk rose with increasing weight: those classified as overweight had an 18 percent higher risk of depression, while obesity was associated with a 52 percent higher risk of depression and a 15 percent higher risk of anxiety.
Looking at life-course trajectories—how weight changed from childhood to adulthood—the researchers identified nine groups and found that adult weight was the dominant predictor of future mental health. Those who were thinner as children and became obese as adults carried the highest risks overall, with a 73 percent higher depression risk and a 33 percent higher anxiety risk compared with individuals who maintained an average and normal weight throughout life. Those who were average in childhood but obese in adulthood also showed elevated risks.
A mediation analysis suggested that adult BMI explained about 45 percent of the association between childhood plumpness and adult depression, and about 31 percent of the link with adult anxiety. This implies that persistent or worsening overweight into adulthood partly accounts for the connection between a heavy childhood and later mental health outcomes.
Crucially, the study found that childhood adiposity did not universally forecast higher mental health risk in later life. Participants who were plumper in childhood but achieved a normal weight in adulthood did not show a statistically significant increase in depression or anxiety, with their risk levels similar to those who were of average size in both childhood and adulthood.
The researchers caution that recalling childhood size decades later may introduce memory bias, and that the UK Biobank cohort predominantly comprises volunteers of European descent, which may limit how broadly the findings apply. They also note that the study combined various medical codes for depression and anxiety rather than separating into subtypes, which could relate to weight in different ways.
The study is titled “Life-course trajectories of body size from childhood to adulthood and risk of incident depression and anxiety: a prospective cohort study,” and the authors are Dong-Run Li, Ke-Ru Li, Bang-Quan Liu, Jia-Cheng Liu, Wen-Rui Zheng, Ting-Ting Gong, Shan-Yan Gao and Qi-Jun Wu.
