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.

BackgroundAutism spectrum disorders (ASDs) are complex neurobiological conditions with poor long-term outcomes and limited treatment options. The microbiota–gut–brain axis indicates a pathway by which the gut microbiota links to ASDs. Fecal microbial transplantation (FMT), whereby the gut microbiota is replaced with that of a healthy individual, shows promise for the treatment of neurobiological conditions. This review examines the current evidence for the use of FMT as a therapeutic for ASD.DiscussionASDs and their associated gastrointestinal symptoms are improved with FMT, potentially due to the engraftment of features of a healthy gut. Longer treatment regimens that include daily maintenance doses appear to be the most effective long-term therapeutic option, with benefits persisting 2 years post-intervention. Evidence is mixed regarding the use of preparatory treatments. Considering the sex bias in ASD research, small sample sizes and the lack of placebo control arms, randomized controlled trials would be of benefit to the evidence base regarding the use of FMT as a therapeutic option for ASD.ConclusionFMT is a promising new therapeutic for ASD, but the evidence base is in its infancy.