Familial confounding of internalising symptoms and obesity in adolescents and young adults; a co-twin analysis

Alexander Charles Campbell; Lucas Calais-Ferreira; Elisabeth Hahn; Frank M Spinath; John L Hopper; Jesse T Young

doi:10.1038/s41366-024-01491-w

Familial confounding of internalising symptoms and obesity in adolescents and young adults; a co-twin analysis

Int J Obes (Lond). 2024 Feb 15. doi: 10.1038/s41366-024-01491-w. Online ahead of print.

Authors

Alexander Charles Campbell^{1

2

3}, Lucas Calais-Ferreira^{4

5

6}, Elisabeth Hahn⁷, Frank M Spinath⁷, John L Hopper⁸, Jesse T Young^{8

4

9

10

11

12}

Affiliations

¹ Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, VIC, Australia. campbell.a1@unimelb.edu.au.
² Centre for Adolescent Health, Murdoch Children's Research Institute, Parkville, VIC, Australia. campbell.a1@unimelb.edu.au.
³ Justice Health Group, School of Population Health, Curtin University, Perth, WA, Australia. campbell.a1@unimelb.edu.au.
⁴ Centre for Adolescent Health, Murdoch Children's Research Institute, Parkville, VIC, Australia.
⁵ Justice Health Group, School of Population Health, Curtin University, Perth, WA, Australia.
⁶ Centre for Mental Health and Community Wellbeing, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, VIC, Australia.
⁷ Department of Psychology, Saarland University, Saarbruecken, Germany.
⁸ Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Parkville, VIC, Australia.
⁹ School of Population and Global Health, The University of Western Australia, Perth, WA, Australia.
¹⁰ National Drug Research Institute, Curtin University, Perth, WA, Australia.
¹¹ Institute for Mental Health Policy Research, Centre for Addiction and Mental Health, Toronto, OC, Canada.
¹² Dalla Lana School of Public Health, University of Toronto, Toronto, OC, Canada.

PMID: 38360935
DOI: 10.1038/s41366-024-01491-w

Abstract

Background: Obesity and internalising disorders, including depression and anxiety, often co-occur. There is evidence that familial confounding contributes to the co-occurrence of internalising disorders and obesity in adults. However, its impact on this association among young people is unclear. Our study investigated the extent to which familial factors confound the association between internalising disorders and obesity in adolescents and young adults.

Subjects/methods: We used a matched co-twin design to investigate the impact of confounding by familial factors on associations between internalising symptoms and obesity in a sample of 4018 twins aged 16 to 27 years.

Results: High levels of internalising symptoms compared to low levels increased the odds of obesity for the whole cohort (adjusted odds ratio [AOR] = 3.1, 95% confidence interval [CI]: 1.5, 6.8), and in females (AOR = 4.1, 95% CI 1.5, 11.1), but not in males (AOR = 2.8 95% CI 0.8, 10.0). We found evidence that internalising symptoms were associated with an increased between-pair odds of obesity (AOR 6.2, 95% CI 1.7, 22.8), using the paired analysis but not using a within-pair association, which controls for familial confounding. Sex-stratified analyses indicated high internalising symptoms were associated with increased between-pair odds of obesity for females (AOR 12.9, 95% CI 2.2, 76.8), but this attenuated to the null using within-pair analysis. We found no evidence of between or within-pair associations for males and weak evidence that sex modified the association between internalising symptoms and obesity (likelihood ratio test p = 0.051).

Conclusions: Some familial factors shared by twins confound the association between internalising symptoms and obesity in adolescent and young adult females. Internalising symptoms and obesity were not associated for adolescent and young adult males. Therefore, prevention and treatment efforts should especially address familial shared determinants of obesity, particularly targeted at female adolescents and young adults with internalising symptoms and those with a family history of these disorders.