A Longitudinal Study on Family Adaptation and Relationship Dynamics in Pediatric Rare Diseases

Rare diseases (RDs) are chronic conditions that often begin in childhood and can have lifelong consequences for affected individuals and their families. In addition to physical health challenges, families frequently face significant psychological and social burdens, including stress, uncertainty about the future, and disruptions in daily life. While prior research has mainly focused on medical aspects of rare diseases, less is known about how families adapt over time and how interactions between children and their caregivers influence psychological outcomes.

This study is based on a theoretical model of family adaptation that integrates individual, relational, and contextual factors. In particular, it focuses on cognitive and emotional processes such as intolerance of uncertainty, illness perceptions, and coping strategies, as well as family-level processes including communication, parenting, and shared experiences of illness ("we-disease"). The study adopts a systemic perspective, recognizing that the well-being of children and caregivers is interdependent and evolves over time.

The project uses a longitudinal design with four assessment waves over a 12-month period, complemented by annual follow-ups. This design allows for the investigation of both stability and change in psychological adjustment. Data will be collected using standardized, validated questionnaires assessing mental health, health-related quality of life, stress, and family functioning. To better capture the child's perspective, a subset of children and adolescents will participate in structured interviews at each time point.

In addition to the longitudinal component, a subgroup of families will participate in an Ecological Sampling Method (ESM) phase. During this two-week period, caregivers will report multiple times per day on their current emotional state, stress levels, worries, perceived uncertainty, and coping responses using a smartphone application. This intensive data collection approach enables the examination of short-term, real-life dynamics and within-person fluctuations that cannot be captured through traditional survey methods.

The study will apply advanced statistical methods to analyze both longitudinal and intensive repeated-measures data. Actor-Partner Interdependence Models (APIM) and related approaches will be used to examine reciprocal relationships between child and caregiver outcomes over time, while multilevel modeling will be used to analyze daily processes captured in the ESM phase. By integrating these approaches, the study aims to identify both long-term adaptation patterns and short-term mechanisms that contribute to psychological adjustment.

The overall goal of the project is to generate a comprehensive understanding of how families adapt to pediatric rare diseases, including identifying risk and protective factors at the individual and family level. The findings are expected to inform the development of targeted psychosocial interventions, improve clinical support for affected families, and contribute to a more holistic approach to rare disease care that addresses both medical and psychosocial needs.

Inclusion criteria

For children and adolescents:

• Diagnosed with an RD listed in Table 2.
• Age between 8 and 18 years.
• Sufficient knowledge of the German language.
• Declaration of informed consent must be signed by at least one legal guardian for all participants under 18; adolescents aged 14 - 17 additionally provide their own written consent.
• Lives at home (defined as sleeping inside of the home for more than four days per week, including weekends).

For parents:

• The child is affected by an RD listed in Table 2.
• The child's age is between 1 and 18 years.
• Sufficient knowledge of the German or English language.
• Availability of the signed declaration of informed consent.
• Only one child with a diagnosed RD.
• Up to two caregivers may participate per child. A stepparent may be included if they reside with the child, defined as spending at least three nights per week (including weekends) in the same household.
• Requirement ESM: Child lives at home (defined as sleeping inside of the home for more than four days per week, including weekends).

Exclusion criteria

For children and adolescents:

• The child is affected by an RD other than listed in Table 2.
• Age under 8 or over 18 years.
• Not sufficient knowledge of the German language.
• Lack of informed consent from at least one legal guardian (required for all participants under 18); and, for adolescents aged 14 - 17, absence of adolescent's own written consent.
• Lives outside of the home (defined as sleeping outside of the home for more than three days per week, including weekends).
• Cognitive impairment.

For parents:

• The child is affected by an RD other than listed in Table 2.
• The child's age is under 1 or over 18 years.
• Not sufficient knowledge of the German nor English language.
• Declaration of informed consent not signed.
• More than one child with a diagnosed RD.
• Requirement ESM: Child lives outside of the home (defined as sleeping outside of the home for more than three days per week, including weekends).