Mental disorders and discrimination: A prospective cohort study of young twin pairs in Germany

Lucas Calais-Ferreira; Gregory Armstrong; Elisabeth Hahn; Giles Newton-Howes; James Foulds; John L Hopper; Frank M Spinath; Paul Kurdyak; Jesse T Young

doi:10.1016/j.ssmph.2024.101622

Mental disorders and discrimination: A prospective cohort study of young twin pairs in Germany

SSM Popul Health. 2024 Feb 7:25:101622. doi: 10.1016/j.ssmph.2024.101622. eCollection 2024 Mar.

Authors

Lucas Calais-Ferreira^{1

2

3}, Gregory Armstrong⁴, Elisabeth Hahn⁵, Giles Newton-Howes⁶, James Foulds⁷, John L Hopper⁸, Frank M Spinath⁵, Paul Kurdyak^{9

10

11

12}, Jesse T Young^{2

8

12

13

14}

Affiliations

¹ Centre for Mental Health and Community Wellbeing, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, Australia.
² Centre for Adolescent Health, Murdoch Children's Research Institute and Royal Children's Hospital, Melbourne, Victoria, Australia.
³ Justice Health Group, School of Population Health, Curtin University, Perth, Western Australia, Australia.
⁴ Nossal Institute for Global Health, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, Australia.
⁵ Department of Psychology, Saarland University, Saarbruecken, Germany.
⁶ Department of Psychological Medicine, University of Otago, Wellington, New Zealand.
⁷ Department of Psychological Medicine, University of Otago, Christchurch, New Zealand.
⁸ Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, Australia.
⁹ ICES, Toronto, Ontario, Canada.
¹⁰ Department of Psychiatry, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
¹¹ Institute of Health Policy, Management and Evaluation, Dalla Lana School of Public Health, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
¹² Centre for Addiction and Mental Health, Toronto, Ontario, Canada.
¹³ School of Population and Global Health, The University of Western Australia, Perth, Western Australia, Australia.
¹⁴ National Drug Research Institute, Curtin University, Perth, Western Australia, Australia.

Abstract

Background: Mental disorders and perceived discrimination share common risk factors. The association between having a mental disorder and experiencing discrimination is well-known, but the extent to which familial factors, such as genetic and shared environmental factors, might confound this association, including sex differences in familial confounding, remains unexplored.

Aims: We investigated potential unmeasured familial confounding in the association between mental disorders and perceived discrimination using a matched twin study design.

Method: We examined data from 2044 same-sex twin pairs (n = 4088) aged 16-25 years from the German population-based study 'TwinLife'. We applied random-effects logistic regression to within-individual and within-and-between pair models of the association between mental disorder and perceived discrimination, and used likelihood ratio tests (LRTs) to compare these models. Multivariable models were adjusted for body mass index, educational attainment, and life satisfaction.

Results: There were 322 (8.1%) participants with a diagnosed mental disorder, and 15% (n = 604) of the cohort reported having experienced discrimination in the previous 12 months. Mental disorder and discrimination were associated in the adjusted within-individual model (adjusted odds ratio = 2.19, 95% confidence interval: 1.42-3.39, P<0.001). However, the within-and-between pair model showed that this association was explained by the within-pair mean (aOR = 4.24, 95% CI: 2.17-8.29, P<0.001) and not the within-pair difference (aOR = 1.26, 95% CI: 0.70-2.28, P = 0.4) of mental disorder. Therefore, this association was mostly explained by familial confounding, which is also supported by the LRTs for the unadjusted and adjusted models (P<0.001 and P = 0.03, respectively). This familial confounding was more prominent for males than females.

Conclusions: Our findings show that the association between mental disorder and discrimination is at least partially explained by unmeasured familial factors. Designing family-based healthcare models and incorporating family members in interventions targeted at ameliorating mental ill-health and experiences of discrimination among adolescents may improve efficacy.

Keywords: Adolescence; Mental health; Social determinants of health; Stigma; Twin study; Youth.