Background: Children and adolescents of so-called 'parents with a mental illness' have a potentially increased risk of developing health problems, as well as experiencing further negative consequences on the way to their adulthood. One option to mitigate or even prevent negative consequences are family-oriented intervention programmes with social support systems. Gaps in health economic knowledge is a barrier to grasp the overall benefit of these programmes. Against this background, this report is intended to inform about existing health economic evidence in this field. Furthermore, we want to raise awareness among health planners and policy makers about the economic and social dimensions of mental illness in families.

Methods: For part 1 of the report, we conducted a systematic review of cost-effectiveness evidence of internationally implemented family-oriented complex interventions focussing on prevention in children and adolescents. In part 2 of the report, we developed an economic evaluation framework to depict short and long-term effects of the parental mental illness for the child and adolescent. In a second step, we discussed possible budget- and resource-relevant impacts resulting from identified effects. As a last step, we analysed to what extent the existing health economic studies in this context have considered the identified consequences and what methodical conclusions can be drawn.

Results: In the course of the systematic search, we identified three health economic studies that analysed three different intervention programmes (two from the UK and one study from the Netherlands). All programmes had the aim to improve parenting with a focus on child development. In summary, two programmes showed mixed results in terms of cost-effectiveness depending on the perspective, subgroup considered or decision-relevant threshold, but cost-effectiveness (efficiency) tended to be present in both of them. In contrast, one programme was cost-effective from all perspectives. Because the studies followed the standard methods of health economic evaluations, they also met most of the quality standards and had only a low to moderate risk of bias.

In part 2 of the report, we were able to identify 39 studies that showed a wide range of possible (health) consequences for children and adolescents due to their parents' mental illness. In addition to individual consequences, parental mental illness is also associated with consequences at the societal level. Resulting costs do not only arise in the health sector. In addition to private costs, costs can also arise in other areas of the public sector that may only occur at a later point in time.

Conclusion: In recent years, there has been increasing evidence that family-oriented complex interventions have significant preventive and therapeutic effects on the health of children and adolescents. However, standard methods of health economic evaluation are limited in assessing intervention programmes of a complex nature. This report attempts to address these limitations and proposes solutions to improve the health economic evaluation methodology in the field of children and adolescents from families with mental illnesses. The application of the methods in their current form could lead to a misjudgement of the cost-effectiveness of such programmes and thus to wrong decisions regarding funding. Finally yet importantly, the report highlights the broad spectrum of economic effects of parental mental illness and the need to prevent them through targeted prevention.