Being the other child - A systematic review on the quality of life and mental health of siblings of children with rare diseases.

Background: Siblings of children with rare diseases play a crucial yet often overlooked role in the family dynamic and their sibling's illness experience. This systematic review aims to synthesize and evaluate existing research on the Quality of Life (QoL) and mental health outcomes of siblings in this unique context.

Methods: We performed a systematic literature search in six databases, including quantitative studies on siblings of children with rare diseases. A total of 37 reports (34 studies) met the inclusion criteria. Siblings' QoL and mental health were compared to normative samples and their siblings with a rare disease. Risk factors for siblings' QoL and mental health were systematically investigated. Moreover, methodological quality and risk of bias were analyzed.

Results: The findings revealed that siblings of children with rare diseases experience reduced QoL and mental health compared to norm data, although results have been mixed. Psychosocial risk factors like parental family stress factors, compared to disease-specific risk factors, play a particular role in the QoL and mental health of siblings of children with rare diseases.

Conclusion: Healthcare providers should consider and address the potential psychosocial impact on QoL and mental health in siblings of children with rare diseases. Additionally, opportunities to bridge existing research gaps and suggestions for advancing theory-driven research in this area will be discussed.