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). I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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. The cohort is maintained by the Finnish Institute for Health and Welfare and approved by the ethical committee of the institute (decision 5/2013).

The details of the IRB/oversight body that provided approval or exemption for the research described are given below: I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

The authors have declared no competing interest. The findings are important in enabling us to recognise target groups and in designing interventions that aim to prevent families with children from falling into economic hardship How this study might affect research, practice or policy

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