Age at separation, residential mobility, and depressive symptoms among twins in late adolescence and young adulthood: a FinnTwin12 cohort study

Objectives Leaving the parental home at an early age represents a major life event for an adolescent and may predispose them to poor mental health. This study aims to examine the effect of age at separation and residential mobility (from residential records) on depressive symptoms among twins in late adolescence and young adulthood. Age at separation of twins in a twin pair was used as a proxy indicator for the age of leaving the parental home Methods The participants (n=3055) are from the FinnTwin12 cohort. Residential mobility consisted of the number and total distance of moves before age 17. First, we used linear regression to assess the association of age at separation and residential mobility with log-transformed General Behavior Inventory (GBI) scores at age 17 and in young adulthood. Then, the mixed model for repeated measures (MMRM) was used to visualize the GBI scores’ trajectory and test the associations, controlling for “baseline” state. Results In the adjusted linear regression, compared to twins separated before age 17, twins who separated in the later three groups all were significantly lower on log-transformed GBI scores at age 17. The two groups of twins who separated after age 19.5 scored lower GBIs in young adulthood. Compared to twins who never moved before age 17, moving twice led to a lower GBI score. In MMRM, twins who separated later all had lower GBI scores in young adulthood. Twins who moved twice or more had lower GBI scores in young adulthood. Conclusion The current study provides valid evidence of the family influence on depressive symptoms in later adolescence and young adulthood. A strong association between residential mobility and depressive symptoms was affirmed, although further research is still needed in the future. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement Data collection was supported by the National Institute on Alcohol Abuse and Alcoholism of the National Institutes of Health under award numbers (R01AA012502 and R01AA015416) and the Academy of Finland (grants 100499, 205585, 118555, 141054, 265240, 263278 and 264146). Data analysis has been supported by the Academy of Finland (grants 312073 and 336823). The content is solely the responsibility of the authors and does not necessarily represent the official views of the funders. This project has partly received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 874724 (Equal-Life). Equal-Life is part of the European Human Exposome Network. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The ethical committee of Helsinki and Uusimaa University Hospital District gave ethical approval for this work The ethical committee of Indiana University gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors