Childhood Body Size Change Linked With Higher Rates of Depression and Anxiety in UK Study

A large UK Biobank analysis has found that adults who remembered being thinner than other children at age 10 and were in the study’s highest adult-size group had the highest rates of later hospital-diagnosed depression and anxiety.

The findings show an association, not proof that a change in body size causes mental health conditions. The study also found that all three groups with higher adult body size had the highest risks, regardless of childhood body size.

What the study found

The research included 447,821 people and followed them for a median of 12.6 years. Participants who already had a depression or anxiety diagnosis when they joined the study were excluded.

Compared with people who reported being about average-sized at age 10 and were in the study’s average adult-size group, those in the thinner-to-higher group had a 90% higher rate of hospital-diagnosed depression. Their hazard ratio was 1.90, with a 95% confidence interval of 1.79 to 2.01.

The same group had a 58% higher rate of hospital-diagnosed anxiety, with a hazard ratio of 1.58 and a 95% confidence interval of 1.48 to 1.68.

In raw numbers, 1,604 of 16,851 people in the thinner-to-higher group, about 9.5%, received a depression diagnosis during follow-up. That compared with 5,321 of 122,455 people, about 4.3%, in the average-to-average group.

The thinner-to-higher group also scored highest on later depression and anxiety questionnaires. These questionnaire results complemented the hospital-record findings but do not change the study’s observational design.

Adult-size groups were relative, not clinical categories

Researchers divided participants into three study-specific adult-size groups using measured height and weight. The highest 16% had an average body mass index of about 35, the middle 51% had an average of about 28, and the lowest 33% had an average of about 23.

These bands were relative to the study population and should not be treated as clinical categories. In this mostly middle-aged sample, two-thirds of participants met the standard definition of overweight or obesity, meaning the study’s average adult-size group was already in the overweight range.

Across the nine combinations of recalled childhood size and adult-size group, the higher adult-size groups generally had the highest risks. For depression, the hazard ratios were 1.90 for thinner-to-higher, 1.82 for plumper-to-higher, and 1.49 for average-to-higher, compared with the average-to-average group.

For anxiety, the corresponding hazard ratios were 1.58, 1.38, and 1.29. People who recalled being thinner at age 10 and remained in the lower adult-size group had a depression rate similar to the reference group, although their anxiety rate was slightly higher.

Possible pathways remain uncertain

Lifestyle habits, high blood pressure, type 2 diabetes, and cardiovascular disease statistically accounted for roughly 22% of the additional risk associated with the thinner-to-higher pattern. This was an exploratory mediation analysis, so it estimates how much of the association may run through these factors; it does not show that they caused the mental health outcomes.

The researchers suggested that changes in self-image, weight stigma, health worries, and metabolic changes could also be relevant. However, the study did not establish these as explanations. The remaining association could reflect unmeasured influences, including childhood poverty, childhood mental health, genetics, weight stigma, or body dissatisfaction.

Why the findings need careful interpretation

Participants were asked at enrollment, when they averaged about 57 years old, to recall whether they had been thinner than average, about average, or plumper than average at age 10. Childhood body size was therefore not measured directly during childhood, and current weight or health could have influenced memory.

The analysis used UK Biobank volunteers of European ancestry. The source notes that these volunteers tend to be healthier and better off than the wider UK population, so the reported percentages should not be treated as population rates.

Hospital records may also have missed milder or untreated depression and anxiety. In addition, symptoms or conditions present before enrollment but not diagnosed could have influenced participants’ weight, habits, or recollections.

The results add to research on how body size across the life course may relate to later health, but they do not show that any individual’s childhood or adult body size determines their mental health.

AI tools were used to assist with the preparation of this article under our editorial standards.