Importance: Mood disorders are associated with increased body weight, especially in females, but it remains unknown when the weight increase starts.
Objectives: To examine sex-specific weight trajectories associated with familial mood disorder risk and determine the age at which youth at familial risk for mood disorders begin to diverge in weight from controls.
Design, setting, and participants: This community-based, single-center, acceleration cohort study of youth at familial risk for mood disorders and controls with yearly follow-ups (mean [SD], 5 [2.1] years) from January 1, 2014, to December 31, 2022, assessed 394 unaffected female and male offspring (aged 3 to 20 years) of parents with or without a mood disorder. Parents with mood (depressive or bipolar) disorders were recruited through adult mental health services. Parents of control participants were matched on age and socioeconomic factors and recruited through acquaintance referrals or schools.
Exposures: The youth in the familial mood risk group had at least 1 parent with a major mood disorder, whereas control youth did not have a parent with a mood disorder.
Main outcomes and measures: Body mass indexes (BMIs) were calculated as weight in kilograms divided by height in meters squared from measured weight and height at annual assessments and then converted to age- and sex-adjusted z scores (zBMIs). Repeated-measure regressions examined the association between zBMI and age in youth at familial risk of mood disorders and controls while accounting for sex. Sensitivity analyses accounted for socioeconomic status, prematurity, and birth weight.
Results: Of 394 participants (mean [SD] age, 11.5 [3.6] years; 203 [51.5%] female), youths at familial risk for mood disorders showed overall no difference in body weight (β = 0.12; 95% CI, 0.01-0.24) from controls. A sex-specific difference was detected, with females at familial risk showing a rapid peripubertal increase in body weight, leading to significantly increased zBMIs at 12 years and older compared with controls (β = 0.57; 95% CI, 0.31-0.82) independent of socioeconomic status, prematurity, or birth weight. Males did not differ from controls at any age.
Conclusions and relevance: In this cohort study, females with a family history of mood disorders were prone to weight gain starting around puberty and predating mood disorder onset. Early interventions aiming to prevent adverse mental and physical outcomes in this vulnerable group need to start in childhood.