Physical and mental health impact of COVID-19 on children, adolescents, and their families: The Collaborative Outcomes study on Health and Functioning during Infection Times - Children and Adolescents (COH-FIT-C&A)

•The collaborative outcome study on health and functioning during infection times (COH-FIT) is a global survey on COVID-19 impact to date, involving more than 230 researchers and 120 institutions across all continents.•COH-FIT is an online anonymous survey, cross-sectional at the individiual level, but longitudinal at the population level, and has a multi-wave structure.•COH-FIT is available in 30 languages, deliberately including linguistic and ethnic minorities. It collects information on health and functioning of adults, but also of children (from 6 years old) and adolescents, via self-report and parental rating questionnaire.•COH-FIT collects both representative sample via polling agencies, and non-representative samples via snowball/non-probability recruiting startegies.•COH-FIT has been collecting over 150,000 responses from over 150 countries, of which 13,000 minors from the six continents from april 26th, 2020 to june 2021. The COVID-19 pandemic has altered daily routines and family functioning, led to closing schools, and dramatically limited social interactions worldwide. Measuring its impact on mental health of vulnerable children and adolescents is crucial. The Collaborative Outcomes study on Health and Functioning during Infection Times (COH-FIT – www.coh-fit.com) is an on-line anonymous survey, available in 30 languages, involving >230 investigators from 49 countries supported by national/international professional associations. COH-FIT has thee waves (until the pandemic is declared over by the WHO, and 6–18 months plus 24–36 months after its end). In addition to adults, COH-FIT also includes adolescents (age 14–17 years), and children (age 6–13 years), recruited via non-probability/snowball and representative sampling and assessed via self-rating and parental rating. Non-modifiable/modifiable risk factors/treatment targets to inform prevention/intervention programs to promote health and prevent mental and physical illness in children and adolescents will be generated by COH-FIT. Co-primary outcomes are changes in well-being (WHO-5) and a composite psychopathology P-Score. Multiple behavioral, family, coping strategy and service utilization factors are also assessed, including functioning and quality of life. Up to June 2021, over 13,000 children and adolescents from 59 countries have participated in the COH-FIT project, with representative samples from eleven countries. Cross-sectional and anonymous design. Evidence generated by COH-FIT will