Children living with a chronic physical condition (CPC) are more likely than their peers without a disease to develop psychological difficulties or disorders (Hysing et al., 2007). To prevent or treat these difficulties and disorders, many psychotherapeutic approaches have been developed and tested. Most of them follow a categorical approach, based on a global diagnosis (e.g., Moreira et al., 2013). Few interventions are conducted from a processual perspective (Nef et al., 2012) studying underlying mechanisms of psychological functioning. Emotions and cognitions represent such underlying processes and play an important role in many psychopathological disorders. These processes can weaken but also protect a child from developing psychological difficulties, depending on whether they are effective or not (Gipson et al., 2006; Hysing et al., 2007; Lahaye et al., 2011). The present research project aims to identify a psychological intervention that builds on knowledge of emotional and cognitive processes, considered as protective and risk factors, to prevent/treat psychological difficulties. The project will be conducted in two parts:

1. The first phase aims to better understand the action mechanisms of psychological interventions, focused on emotional and cognitive difficulties of children with CPCs. First, a systematic review will identify recent literature which reports the efficacy of psychological interventions which focused on emotional and cognitive processes. Second, interviews with experts (e.g., pediatricians, psychiatrists, psychologists, nurses, educators) in the field of CPCs and with parents/families of children with CPCs will be conducted. Individual and focus group meetings will be organized, with the aim of identifying the needs of children, based on clinical and practical knowledge and experience. A third phase will consist of the selection of an intervention that will be based on the results of the first two phases.
2. In the second part (not yet registered), the selected intervention will be set up for a feasibility study (Bowen et al., 2009). For this, a small sample of children will participate in the intervention. Participants will be randomly allocated to an intervention group and a control group. The control group will participate in an alternative intervention (e.g., information on chronic diseases). The exact content of the intervention and its form (number of sessions, duration etc.) will be determined by the focus group. The intervention's efficacy will be evaluated (evaluation of emotional and cognitive processes as well as psychological and physiological health), using a mixed method approach. The results will be analyzed and discussed with the focus group. Limitations and perspectives will be formulated to allow for possible transfer of the intervention for future use or to other areas of psychology (Durlak & DuPre, 2008).

The research project will be conducted as a non-medical intervention study, based on a mixed method and action-research principles (Bradbury & Lifvergren, 2016; Ivankova & Wingo, 2018; Malengreaux et al., 2020; Marshall et al., 2006). It will include a systematic literature review, quantitative (standardized questionnaires, self and hetero-reports) and qualitative measures (dialogues and discussions, semi-directed interviews, audio-recordings, observations, written reports). The effectiveness study of PART II of the research project will be carried out as randomized controlled trial but is not described in this registration.

PART 1

Phase I.a:

A systematic literature review is conducted by all investigators (researchers) in order to better understand action mechanisms of psychological interventions for children with chronic diseases (registered in PROSPERO: CRD42021233505).

Phase I.b:

• Individual semi-structured qualitative interviews will be conducted by one or two investigators to explore the following questions: Which are emotional and cognitive difficulties and resources in children with CPC? Which are the emotional and cognitive needs of children with CPC? How are these/can these be addressed?
• One or several focus groups will be created. They will be composed of different experts in the domain of CPCs (health care professionals, families, researchers, etc.). Per group, one or several meetings will be organized, depending on participants' availabilities. The meetings will be conducted by one or two investigators who will use semi-structured interview techniques to explore the following questions: Which are emotional and cognitive difficulties and resources in children with CPC? Which are the emotional and cognitive needs of children with CPC? How are these/can these be addressed?

PART II will consist of a feasibility and an effectiveness study of the intervention. For both studies, the selected intervention will be implemented, based on scientific, rigorous methods, and be evaluated with different quantitative and qualitative measures. PART II will rely on PART I. Thus, it will be described in another registration after completion of PART I.

Inclusion criteria:

The participant

• is a health care professional in the domain of pediatric chronic diseases or parents/family members/tutors of a child with CPC, aged 8-12 years OR
• is in regular contact with children with a chronic physical condition who are between 8 and 12-years-old.
• speak fluently French

Exclusion Criteria:

• Health care professionals who are not in regular contact with children, 8 to 12 years- old, with a chronic physical condition
• Parents with a child with CPC who is not 8 to 12 years old
• Participants who do not speak French