Puberty Timing Tied to Eating Disorder Risk in 13,208 Danish Teens

Adolescents whose bodies developed ahead of or behind their peers had higher odds of eating disorder diagnoses and body-image pathology than those who developed on schedule, according to a Danish cohort study published Monday in the Journal of Eating Disorders. The researchers followed 13,208 teenagers and found that the timing of puberty mattered more consistently than its speed.

The study adds a developmental marker to a short list of early warning signs clinicians use for eating disorders, which typically emerge during or just after puberty. It also extends the question to boys, a group largely absent from earlier longitudinal work on the subject.

How the cohort was built

The data come from the Puberty Cohort inside the Danish National Birth Cohort, a national study that has followed children born between 1996 and 2002 and their mothers. Rather than asking participants once, years later, to recall when puberty happened, the researchers collected self-assessments every six months through adolescence: Tanner staging for breast, genital and pubic hair development, age at menarche in girls, and age at first ejaculation and voice break in boys.

Those repeated measurements let the team fit a non-linear mixed-effects growth model to each child and sort participants into early/slow, average, or late/fast trajectories for each milestone separately.

Outcomes came from two sources. Clinically diagnosed anorexia nervosa and bulimia nervosa were pulled from the Danish National Patient Register, which captures diagnoses made anywhere in the national health system. Self-reported anorexia, bulimia, binge eating disorder and muscle dysmorphia symptoms were collected at the cohort's 18-year follow-up. Associations were estimated as adjusted odds ratios from logistic regression, with adjustment for a set of confounders including sociodemographic and mental health history variables.

In girls, both directions carried risk

The clearest findings involved anorexia nervosa and the timing of pubic hair development. Girls whose pubic hair arrived early had 3.06 times the odds of a clinical anorexia diagnosis (95% CI, 1.07–8.74); girls whose development came late had 2.43 times the odds (95% CI, 1.02–5.79), both compared with average timing.

Self-reported anorexia followed a similar pattern, concentrated on late development: late breast development carried an odds ratio of 3.86 (95% CI, 1.84–8.07), late pubic hair 2.41 (95% CI, 1.07–5.44), and late menarche 3.10 (95% CI, 1.45–6.63).

Binge eating disorder ran the other way. Early timing of breast development, pubic hair and menarche was associated with higher odds of self-reported binge eating, which the authors read as a possible consequence of rapid body-fat accumulation arriving before a girl's peer group catches up.

The tempo findings were messier. Fast pubic hair development was linked to higher odds of clinical anorexia and self-reported binge eating but lower odds of self-reported anorexia — a contradiction the authors flag rather than explain away. Their conclusion is that timing, not tempo, is the more dependable signal.

Boys were not spared

Muscle dysmorphia, a preoccupation with perceived insufficient muscularity that drives compulsive training, restrictive eating and sometimes steroid use, has been studied far less than eating disorders in girls. In this cohort, both ends of the timing distribution were associated with more symptoms: early first ejaculation carried an odds ratio of 1.96 (95% CI, 1.06–3.63), and late genital development 1.88 (95% CI, 1.11–3.20).

Tempo in boys showed no consistent association.

What the numbers can and cannot support

The confidence intervals are wide, and some are close to the null. The anorexia findings for early and late pubic hair timing, for instance, have lower bounds of 1.07 and 1.02 — statistically significant, but compatible with effects far smaller than the point estimates suggest. The sample, while large, comes from a single Danish birth cohort, and self-reported outcomes at 18 introduce recall and reporting error. An observational cohort can show that off-time development and eating pathology travel together; it cannot say that one causes the other.

What it does support is a practical point. Pediatricians and school health staff already track growth and pubertal staging. A teenager who is conspicuously early or late relative to classmates is visible in exactly the settings where eating disorder symptoms first surface, and the study suggests that visibility is worth acting on.

"Earlier and later pubertal timing may help identify adolescents who could benefit from closer monitoring for early signs of EDs and muscle dysmorphia symptoms," the authors write. Lead author Anne Marie Ladehoff Thomsen and colleagues are based in the Department of Public Health at Aarhus University.

For families, the clinical takeaway is that timing is a risk marker rather than a diagnosis. Treatment for eating disorders begins with medical and psychiatric assessment, and the level of care — outpatient therapy, an intensive outpatient program or residential treatment — depends on medical stability, symptom frequency and how long the illness has run. Family-based treatment remains the best-supported approach for adolescents with anorexia.

Boys with muscle dysmorphia often reach services late, or never, because the behavior reads as discipline rather than illness. The Danish data suggest that an off-schedule puberty is one moment when a clinician can ask.