Editorial Perspective: When is a 'small effect' actually large and impactful?

Reporting of effect sizes is standard practice in psychology and psychiatry research. However, interpretation of these effect sizes can be meaningless or misleading - in particular, the evaluation of specific effect sizes as 'small', 'medium' and 'large' can be inaccurate depending on the research context. A real-world example of this is research into the mental health of children and young people during the COVID-19 pandemic. Evidence suggests that clinicians and services are struggling with increased demand, yet population studies looking at the difference in mental health before and during the pandemic report effect sizes that are deemed 'small'. In this short review, we utilise simulations to demonstrate that a relatively small shift in mean scores on mental health measures can indicate a large shift in the number of cases of anxiety and depression when scaled up to an entire population. This shows that 'small' effect sizes can in some contexts be large and impactful.

The benefits of continuing patient and public involvement as part of a randomised controlled trial during the Covid-19 global pandemic

Patient and public involvement (PPI) in clinical research strengthens the quality and relevance of research, and has been crucial to ensure that researchers continue to investigate relevant and important topics during the global Covid-19 pandemic. The MICE (Mental Health Intervention for Children with Epilepsy) randomised controlled trial relies upon PPI to steer the direction and delivery of the trial, and the PPI Research Advisory Group (RAG) adapted to remote online meetings during the pandemic. This article first describes how the PPI RAG supported the research trial during the course of the pandemic, particularly with key trial stages of recruitment, retention and follow-up. It considers how the PPI tasks were adapted to ensure that they remained meaningful throughout this period, particularly for children and young people. Second, the article explores the acceptability of PPI in research using teleconferencing methods, via a co-produced survey of the PPI group members. Survey results indicated that, while participants valued face-to-face meetings, having remote PPI meetings was preferable to having nothing. There was some suggestion that teleconferencing platforms make it challenging for reserved members of the group, and for children, to contribute. Our findings emphasise the importance of continuing PPI even when circumstances are sub-optimal. We hope that our findings will contribute to the wider conversation about what makes PPI effective, particularly in a digital world. [ FROM AUTHOR] Copyright of Research for All is the property of UCL Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

Long COVID-six months of prospective follow-up of changes in symptom profiles of non-hospitalised children and young people after SARS-CoV-2 testing: A national matched cohort study (The CLoCk) study.

BACKGROUND: Little is known about the prevalence and natural trajectory of post-COVID symptoms in young people, despite very high numbers of young people having acute COVID. To date, there has been no prospective follow-up to establish the pattern of symptoms over a 6-month time period. METHODS: A non-hospitalised, national sample of 3,395 (1,737 SARS-COV-2 Negative;1,658 SARS-COV-2 Positive at baseline) children and young people (CYP) aged 11-17 completed questionnaires 3 and 6 months after PCR-confirmed SARS-CoV-2 infection between January and March 2021 and were compared with age, sex and geographically-matched test-negative CYP. RESULTS: Three months after a positive SARS-CoV-2 PCR test, 11 of the 21 most common symptoms reported by >10% of CYP had reduced. There was a further decline at 6 months. By 3 and 6 months the prevalence of chills, fever, myalgia, cough and sore throat of CYP who tested positive for SARS-CoV-2 reduced from 10-25% at testing to <3%. The prevalence of loss of smell declined from 21% to 5% at 3 months and 4% at 6 months. Prevalence of shortness of breath and tiredness also declined, but at a lower rate. Among test-negatives, the same common symptoms and trends were observed at lower prevalence's. Importantly, in some instances (shortness of breath, tiredness) the overall prevalence of specific individual symptoms at 3 and 6 months was higher than at PCR-testing because these symptoms were reported in new cohorts of CYP who had not reported the specific individual symptom previously. CONCLUSIONS: In CYP, the prevalence of specific symptoms reported at time of PCR-testing declined with time. Similar patterns were observed among test-positives and test-negatives and new symptoms were reported six months post-test for both groups suggesting that symptoms are unlikely to exclusively be a specific consequence of SARS-COV-2 infection. Many CYP experienced unwanted symptoms that warrant investigation and potential intervention.

Annual Research Review: The impact of Covid-19 on psychopathology in children and young people worldwide: systematic review of studies with pre- and within-pandemic data.

BACKGROUND: The high volume and pace of research has posed challenges to researchers, policymakers and practitioners wanting to understand the overall impact of the pandemic on children and young people's mental health. We aimed to search for and review the evidence from epidemiological studies to answer the question: how has mental health changed in the general population of children and young people? METHODS: Four databases (Medline, CINAHL, EMBASE and PsychINFO) were searched in October 2021, with searches updated in February 2022. We aimed to identify studies of children or adolescents with a mean age of 18 years or younger at baseline, that reported change on a validated mental health measure from prepandemic to during the pandemic. Abstracts and full texts were double-screened against inclusion criteria and quality assessed using a risk of bias tool. Studies were narratively synthesised, and meta-analyses were performed where studies were sufficiently similar. RESULTS: 6917 records were identified, and 51 studies included in the review. Only four studies had a rating of high quality. Studies were highly diverse in terms of design, setting, timing in relation to the pandemic, population, length of follow-up and choice of measure. Methodological heterogeneity limited the potential to conduct meta-analyses across studies. Whilst the evidence suggested a slight deterioration on some measures, overall, the findings were mixed, with no clear pattern emerging. CONCLUSIONS: Our findings highlight the need for a more harmonised approach to research in this field. Despite the sometimes-inconsistent results of our included studies, the evidence supports existing concerns about the impact of Covid-19 on children's mental health and on services for this group, given that even small changes can have a significant impact on provision at population level. Children and young people must be prioritised in pandemic recovery, and explicitly considered in planning for any future pandemic response.

A cross-sectional study of the health of emerging young adults in England following a COVID-19 infection

Purpose This study describes long COVID symptomatology in a national sample of 18–20-year-olds with PCR-confirmed SARS-CoV-2 and matched test-negative controls in England. Symptoms in 18-20-year-olds were compared to younger adolescents (aged 11-17 years) and all adults (18+). Methods A national database was used to identify SARS-CoV-2 PCR-positive 18–20-year-olds and test-negative controls matched by time of test, age, gender and geographical region. Participants were invited to complete a questionnaire about their health retrospectively at time of test and also when completing the questionnaire. Comparison cohorts included Children and Young People with Long COVID and Real-time Assessment of Community Transmission studies. Results Of 14,986 people invited, 1,001 were included in the analysis (562 test-positive;440 test-negative). At testing, 46.5% of test-positives and 16.4% of test-negatives reported at least one symptom. At the time of questionnaire completion (median 7 months post-testing), 61.5% of test-positives and 47.5% of test-negatives reported one or more symptoms. The most common symptoms were similar amongst test-positives and test-negatives and included tiredness (44.0%;35.7%), shortness of breath (28.8%;16.3%) and headaches (13.7%;12.0%). Prevalence rates were similar to those reported by 11-17-year-olds (66.5%) and higher than those reported in all adults (37.7%). For 18-20-year-olds, there was no significant difference in health-related quality of life and wellbeing (p>0.05). However, test-positives reported being significantly more tired than test-negatives (p=0.04). Conclusions Seven months after PCR test, a high proportion of test-positive and test-negative 18-20-year-olds reported similar symptoms to each other and to those experienced by younger and older counterparts.

A Cross-Sectional Study of the Health of Emerging Young Adults in England Following a COVID-19 Infection.

PURPOSE: This study describes long COVID symptomatology in a national sample of 18- to 20-year-olds with Polymerase Chain Reaction (PCR)-confirmed Severe acute respiratory syndrome coronavirus 2 (SARS­CoV­2) and matched test-negative controls in England. Symptoms in 18- to 20-year-olds were compared to symptoms in younger adolescents (aged 11-17 years) and all adults (18+). METHODS: A national database was used to identify SARS-CoV-2 PCR-positive 18- to 20-year-olds and test-negative controls matched by time of test, age, gender, and geographical region. Participants were invited to complete a questionnaire about their health retrospectively at time of test and also when completing the questionnaire. Comparison cohorts included children and young people with long COVID and REal-time Assessment of Community Transmission studies. RESULTS: Of 14,986 people invited, 1,001 were included in the analysis (562 test-positive; 440 test-negative). At testing, 46.5% of test-positives and 16.4% of test-negatives reported at least one symptom. At the time of questionnaire completion (median 7 months post-testing), 61.5% of test-positives and 47.5% of test-negatives reported one or more symptoms. The most common symptoms were similar amongst test-positives and test-negatives and included tiredness (44.0%; 35.7%), shortness of breath (28.8%; 16.3%), and headaches (13.7%; 12.0%). Prevalence rates were similar to those reported by 11-17-year-olds (66.5%) and higher than those reported in all adults (37.7%). For 18- to 20-year-olds, there was no significant difference in health-related quality of life and well-being (p > .05). However, test-positives reported being significantly more tired than test-negatives (p = .04). DISCUSSION: Seven months after PCR test, a high proportion of test-positive and test-negative 18- to 20-year-olds reported similar symptoms to each other and to those experienced by younger and older counterparts.

Post-COVID-19 condition at 6 months and COVID-19 vaccination in non-hospitalised children and young people.

OBJECTIVES: To describe the physical and mental health of children and young people (CYP) 6 months after infection with SARS-CoV-2 and explore whether this varies by COVID-19 vaccination. DESIGN: A non-hospitalised, national cohort of people aged 11-17 years old with PCR-confirmed SARS-CoV-2 infection and PCR negatives matched at study invitation, by age, sex, region and date of testing who completed questionnaires 6 months after PCR testing. The questionnaire included 21 symptoms and standardised scales (eg, EQ-5D-Y and Chalder Fatigue Scale). RESULTS: 6407 test-positive and 6542 test-negative CYP completed the 6-month questionnaire: 60.9% of test-positive vs 43.2% of test-negative CYP reported at least one symptom 6 months post-test; 27.6% of test-positive vs 15.9% of test-negative CYP reported 3+ symptoms. Common symptoms at 6 months were tiredness and shortness of breath among both test-positive and test-negative CYP; however, the prevalence of both was higher in test-positive (38.4% and 22.8%, respectively) compared with test-negative CYP (26.7% and 10.9%, respectively). 24.5% test-positive vs 17.8% test-negative CYP met the Delphi research definition of long COVID. Mental health, well-being, fatigue and health-related quality of life scores were similar among test-positive and test-negative CYP 6 months post-test. Similarly, symptomatology was similar among COVID-19-vaccinated and COVID-19-unvaccinated test-positive and test-negative CYP. CONCLUSIONS: Six-months post-PCR testing, CYP who tested positive for SARS-CoV-2 had similar symptoms to those who tested negative, but test-positive CYP had higher symptom prevalence. Mental health, well-being, fatigue and health-related quality of life were similar among test-positive and test-negative CYP, and symptoms at 6 months were similar in COVID-19 vaccinated and unvaccinated. TRIAL REGISTRATION NUMBER: ISRCTN 34804192.

Predictive model for long COVID in children 3 months after a SARS-CoV-2 PCR test.

BACKGROUND: To update and internally validate a model to predict children and young people (CYP) most likely to experience long COVID (i.e. at least one impairing symptom) 3 months after SARS-CoV-2 PCR testing and to determine whether the impact of predictors differed by SARS-CoV-2 status. METHODS: Data from a nationally matched cohort of SARS-CoV-2 test-positive and test-negative CYP aged 11-17 years was used. The main outcome measure, long COVID, was defined as one or more impairing symptoms 3 months after PCR testing. Potential pre-specified predictors included SARS-CoV-2 status, sex, age, ethnicity, deprivation, quality of life/functioning (five EQ-5D-Y items), physical and mental health and loneliness (prior to testing) and number of symptoms at testing. The model was developed using logistic regression; performance was assessed using calibration and discrimination measures; internal validation was performed via bootstrapping and the final model was adjusted for overfitting. RESULTS: A total of 7139 (3246 test-positives, 3893 test-negatives) completing a questionnaire 3 months post-test were included. 25.2% (817/3246) of SARS-CoV-2 PCR-positives and 18.5% (719/3893) of SARS-CoV-2 PCR-negatives had one or more impairing symptoms 3 months post-test. The final model contained SARS-CoV-2 status, number of symptoms at testing, sex, age, ethnicity, physical and mental health, loneliness and four EQ-5D-Y items before testing. Internal validation showed minimal overfitting with excellent calibration and discrimination measures (optimism-adjusted calibration slope: 0.96575; C-statistic: 0.83130). CONCLUSIONS: We updated a risk prediction equation to identify those most at risk of long COVID 3 months after a SARS-CoV-2 PCR test which could serve as a useful triage and management tool for CYP during the ongoing pandemic. External validation is required before large-scale implementation.

Natural course of health and well-being in non-hospitalised children and young people after testing for SARS-CoV-2: a prospective follow-up study over 12 months.

Background: Despite high numbers of children and young people (CYP) having acute COVID, there has been no prospective follow-up of CYP to establish the pattern of health and well-being over a year following infection. Methods: A non-hospitalised, national sample of 5086 (2909 SARS-COV-2 Positive; 2177 SARS-COV-2 Negative at baseline) CYP aged 11-17 completed questionnaires 6- and 12-months after PCR-tests between October 2020 and March 2021 confirming SARS-CoV-2 infection (excluding CYP with subsequent (re)infections). SARS-COV-2 Positive CYP was compared to age, sex and geographically-matched test-negative CYP. Findings: Ten of 21 symptoms had a prevalence less than 10% at baseline, 6- and 12-months post-test in both test-positives and test-negatives. Of the other 11 symptoms, in test-positives who had these at baseline, the prevalence of all symptoms declined greatly by 12-months. For CYP first describing one of these at 6-months, there was a decline in prevalence by 12-months. The overall prevalence of 9 of 11 symptoms declined by 12-months. As many CYP first described shortness of breath and tiredness at either 6- or 12-months, the overall prevalence of these two symptoms in test-positives appeared to increase by 6-months and increase further by 12-months. However, within-individual examination demonstrated that the prevalence of shortness of breath and tiredness actually declined in those first describing these two symptoms at either baseline or 6-months. This pattern was also evident for these two symptoms in test-negatives. Similar patterns were observed for validated measures of poor quality of life, emotional and behavioural difficulties, poor well-being and fatigue. Moreover, broadly similar patterns and results were noted for the sub-sample (N = 1808) that had data at baseline, 3-, 6- and 12-months post-test. Interpretation: In CYP, the prevalence of adverse symptoms reported at the time of a positive PCR-test declined over 12-months. Some test-positives and test-negatives reported adverse symptoms for the first time at six- and 12-months post-test, particularly tiredness, shortness of breath, poor quality of life, poor well-being and fatigue suggesting they are likely to be caused by multiple factors. Funding: NIHR/UKRI (ref: COVLT0022).

Digital access constraints predict worse mental health among adolescents during COVID-19.

The COVID-19 pandemic and ensuing social restrictions disrupted young people's social interactions and resulted in several periods during which school closures necessitated online learning. We hypothesised that digitally excluded young people would demonstrate greater deterioration in their mental health than their digitally connected peers during this time. We analysed representative mental health data from a sample of UK 10-15-year-olds (N = 1387) who completed a mental health inventory in 2017-2019 and thrice during the pandemic (July 2020, November 2020 and March 2021). We employed longitudinal modelling to describe trajectories of adolescent mental health for participants with and without access to a computer or a good internet connection for schoolwork. Adolescent mental health symptoms rose early in the COVID-19 pandemic, with the highest mean Total Difficulties score around December 2020. The worsening and subsequent recovery of mental health during the pandemic was greatly pronounced among those without access to a computer, although we did not find evidence for a similar effect among those without a good internet connection. We conclude that lack of access to a computer is a tractable risk factor that likely compounds other adversities facing children and young people during periods of social isolation or educational disruption.

The COVID-19 pandemic and child and adolescent mental health—what has been learned and lessons for the future

Children and young people have arguably been the group most affected by the societal response to COVID-19. The quality of the evidence base globally on the impact of COVID-19 on child mental health is highly variable. However, it is clear that the pandemic has been associated with an overall deterioration in mental health in children and young people at a population level, but with evidence of unequal impacts on different groups. This chapter draws on the available evidence at the time of writing to provide an overview of a spectrum of topics, from the effects of acute COVID-19 illness on children and young people, to the impact on at-risk groups, and access to mental health services and education during the pandemic, as well as discussing the implications and recommendations for research, practice, and policy.

Are children who need help in contact with services?/what do we know about patterns of service contact?

BackgroundEven prior to the Covid-19 pandemic, referrals to child and adolescent mental health services have been rising, in conjunction with increased focus and demand on school based mental health support. This study investigates whether children with mental health problems are becoming more or less likely to be in contact with sources of help, examining secular trends using NHS Digital’s national child mental health surveys. These are the only repeated national epidemiological surveys to include standardised psychiatric diagnostic assessments in cross-sectional community samples of children and young people, using stratified probability sampling.Data Mental Health of Children and Young People (MHCYP) 2017 and British Child and Adolescent Mental Health Surveys 1999 and 2004 (BCAMHS), including ICD-10 psychiatric diagnoses from the validated Development and Wellbeing Assessment and parent and young person reported mental-health-related contact with a range of public sector services.MethodsDescriptive and trend analyses (using Stata v.17) of prevalence of service contact in relation to diagnosis amongst participants in 1999, 2004 and 2017, using survey weights to take account of selection probabilities and non response. Analysis is ongoing, early analyses of 2017 data are presented in this .ResultsIn MHCYP 2017 (n=7,654;5 to 19 years;mean age 11.2;49.7% female), of those with a diagnosis, a quarter (24.9%) reported contact with specialist mental health services, and 67.8% reported mental health-related contact with any education, health or social care service. In 5 to 16 year olds, males were more likely to have contact than females (75.1%, 95% CI 70.5–79.1% versus 64.3%, 95% CI 58.7–69.6%, p=0.0025). In 17 to 19 year olds, levels of service contact were higher amongst females (59.0%, 95% 48.8–68.4%) than males (47.8%, 95% CI 34.4–61.7%), although confidence intervals for estimates overlapped.ConclusionWhilst most participants with a diagnosis reported some type of service contact, only a quarter had contact with a specialist service (similar to the proportion reported in BCAMHS 2004). There were also gender and age differences in patterns of contact. Analyses in progress are examining trends in contact as well as trends in inequalities in contact to identify groups who may be under-served. Given that Covid-19 is likely to have amplified existing inequalities, and has impacted child mental health at a population level, our analyses will incorporate data from MHCYP 2020 & 2021 once these become available.

Effectiveness and cost-effectiveness of universal school-based mindfulness training compared with normal school provision in reducing risk of mental health problems and promoting well-being in adolescence: the MYRIAD cluster randomised controlled trial.

BACKGROUND: Systematic reviews suggest school-based mindfulness training (SBMT) shows promise in promoting student mental health. OBJECTIVE: The My Resilience in Adolescence (MYRIAD) Trial evaluated the effectiveness and cost-effectiveness of SBMT compared with teaching-as-usual (TAU). METHODS: MYRIAD was a parallel group, cluster-randomised controlled trial. Eighty-five eligible schools consented and were randomised 1:1 to TAU (43 schools, 4232 students) or SBMT (42 schools, 4144 students), stratified by school size, quality, type, deprivation and region. Schools and students (mean (SD); age range=12.2 (0.6); 11-14 years) were broadly UK population-representative. Forty-three schools (n=3678 pupils; 86.9%) delivering SBMT, and 41 schools (n=3572; 86.2%) delivering TAU, provided primary end-point data. SBMT comprised 10 lessons of psychoeducation and mindfulness practices. TAU comprised standard social-emotional teaching. Participant-level risk for depression, social-emotional-behavioural functioning and well-being at 1 year follow-up were the co-primary outcomes. Secondary and economic outcomes were included. FINDINGS: Analysis of 84 schools (n=8376 participants) found no evidence that SBMT was superior to TAU at 1 year. Standardised mean differences (intervention minus control) were: 0.005 (95% CI -0.05 to 0.06) for risk for depression; 0.02 (-0.02 to 0.07) for social-emotional-behavioural functioning; and 0.02 (-0.03 to 0.07) for well-being. SBMT had a high probability of cost-effectiveness (83%) at a willingness-to-pay threshold of £20 000 per quality-adjusted life year. No intervention-related adverse events were observed. CONCLUSIONS: Findings do not support the superiority of SBMT over TAU in promoting mental health in adolescence. CLINICAL IMPLICATIONS: There is need to ask what works, for whom and how, as well as considering key contextual and implementation factors. TRIAL REGISTRATION: Current controlled trials ISRCTN86619085. This research was funded by the Wellcome Trust (WT104908/Z/14/Z and WT107496/Z/15/Z).

Why Is Non-suicidal Self-injury More Common in Women? Mediation and Moderation Analyses of Psychological Distress, Emotion Dysregulation, and Impulsivity.

OBJECTIVE: Non-suicidal self-injury (NSSI) appears to be more common among women than men, though the underlying reasons for this remain unclear. In a community sample of young adults (N = 996, aged 18-33) assessed during the COVID-19 pandemic, we investigated alternative explanation for the NSSI prevalence gap: are women more likely to experience the feelings which lead to NSSI as a coping strategy, or does this prevalence gap result from differences in how men and women respond to distress? METHODS: Cross-sectional mediation and moderation analyses tested how self-reported psychological distress (K10), emotion dysregulation (DERS), and impulsivity (UPPS-P) may contribute to a higher prevalence of NSSI among women. RESULTS: Women were twice as likely as men to report past-year NSSI (14.47% versus 7.78%, OR = 2.00, 95% CI [1.29, 3.13]). Women reported significantly higher psychological distress and significantly lower sensation seeking and positive urgency than men. Psychological distress partially statistically mediated the relationship between gender and past-year NSSI. Gender did not significantly moderate associations between psychological distress, emotion dysregulation, or impulsivity and past-year NSSI. Past-year NSSI prevalence did not significantly decrease with age and we found no significant age by gender interaction. CONCLUSIONS: Greater levels of NSSI in young women are partly explained by their greater levels of psychological distress, but not by differences in how men and women respond to this distress. Given similar levels of psychological distress, emotion dysregulation, and impulsivity, women and men are similarly likely to experience NSSI. HighlightsWomen aged 18-33 were significantly more likely to report past-year NSSI than menWomen's greater psychological distress contributed to their higher NSSI prevalenceVariables investigated here were similarly associated with NSSI in men and women.

Impact of COVID-19 on mental health research: is this the breaking point?

There are many structural problems facing the UK at present, from a weakened National Health Service to deeply ingrained inequality. These challenges extend through society to clinical practice and have an impact on current mental health research, which was in a perilous state even before the coronavirus pandemic hit. In this editorial, a group of psychiatric researchers who currently sit on the Academic Faculty of the Royal College of Psychiatrists and represent the breadth of research in mental health from across the UK discuss the challenges faced in academic mental health research. They reflect on the need for additional investment in the specialty and ask whether this is a turning point for the future of mental health research.

Physical and mental health 3 months after SARS-CoV-2 infection (long COVID) among adolescents in England (CLoCk): a national matched cohort study.

BACKGROUND: We describe post-COVID symptomatology in a non-hospitalised, national sample of adolescents aged 11-17 years with PCR-confirmed SARS-CoV-2 infection compared with matched adolescents with negative PCR status. METHODS: In this national cohort study, adolescents aged 11-17 years from the Public Health England database who tested positive for SARS-CoV-2 between January and March, 2021, were matched by month of test, age, sex, and geographical region to adolescents who tested negative. 3 months after testing, a subsample of adolescents were contacted to complete a detailed questionnaire, which collected data on demographics and their physical and mental health at the time of PCR testing (retrospectively) and at the time of completing the questionnaire (prospectively). We compared symptoms between the test-postive and test-negative groups, and used latent class analysis to assess whether and how physical symptoms at baseline and at 3 months clustered among participants. This study is registered with the ISRCTN registry (ISRCTN 34804192). FINDINGS: 23 048 adolescents who tested positive and 27 798 adolescents who tested negative between Jan 1, 2021, and March 31, 2021, were contacted, and 6804 adolescents (3065 who tested positive and 3739 who tested negative) completed the questionnaire (response rate 13·4%). At PCR testing, 1084 (35·4%) who tested positive and 309 (8·3%) who tested negative were symptomatic and 936 (30·5%) from the test-positive group and 231 (6·2%) from the test-negative group had three or more symptoms. 3 months after testing, 2038 (66·5%) who tested positive and 1993 (53·3%) who tested negative had any symptoms, and 928 (30·3%) from the test-positive group and 603 (16·2%) from the test-negative group had three or more symptoms. At 3 months after testing, the most common symptoms among the test-positive group were tiredness (1196 [39·0%]), headache (710 [23·2%]), and shortness of breath (717 [23·4%]), and among the test-negative group were tiredness (911 [24·4%]), headache (530 [14·2%]), and other (unspecified; 590 [15·8%]). Latent class analysis identified two classes, characterised by few or multiple symptoms. The estimated probability of being in the multiple symptom class was 29·6% (95% CI 27·4-31·7) for the test-positive group and 19·3% (17·7-21·0) for the test-negative group (risk ratio 1·53; 95% CI 1·35-1·70). The multiple symptoms class was more frequent among those with positive PCR results than negative results, in girls than boys, in adolescents aged 15-17 years than those aged 11-14 years, and in those with lower pretest physical and mental health. INTERPRETATION: Adolescents who tested positive for SARS-CoV-2 had similar symptoms to those who tested negative, but had a higher prevalence of single and, particularly, multiple symptoms at the time of PCR testing and 3 months later. Clinicians should consider multiple symptoms that affect functioning and recognise different clusters of symptoms. The multiple and varied symptoms show that a multicomponent intervention will be required, and that mental and physical health symptoms occur concurrently, reflecting their close relationship. FUNDING: UK Department of Health and Social Care, in their capacity as the National Institute for Health Research, and UK Research and Innovation.

Debate: Is there a true global children and young people's mental health crisis, fact or fiction?

Following COVID-19, there has been increasing concern about the well-being of children and young people across the United Kingdom; however, our major problem is the lack of robust data. We discuss emerging research capturing the impact of restrictions and experiences of COVID-19 on children and young people. We suggest further and more detailed analysis is urgently required to inform an evidence-based response. We conclude that although most of the UK's kids are probably OK, it is essential that those who are in need of support receive timely and informed intervention.