Internet-based cognitive-behavioural therapy (iCBT) is effective for subthreshold depression. However, which skills provided in iCBT packages are more effective than others is unclear. Such knowledge can inform construction of more effective and efficient iCBT programmes.

Digital interventions based on cognitive-behavioural therapy (iCBT) is associated with reductions in suicidal ideation. However, fine-grained analyses of effects and potential effect-moderating variables are missing. This study aimed to investigate the effectiveness of iCBT on suicidal ideation, effect moderators, effects on suicide attempts and predictors of adherence.

The WHO's Mental Health Gap Action Programme Intervention Guide (mhGAP-IG) has been widely used in low and middle-income countries. We reviewed literature describing interventions and training programmes beyond the mhGAP-IG, in primary healthcare (PHC) and community-based healthcare (CBH).

Most people with mental disorders in communities exposed to adversity in low-income and middle-income countries (LMICs) do not receive effective care. Digital mental health interventions are scalable when digital access is adequate, and can be safely delivered during the COVID-19 pandemic.

Non-serious adverse events (NSAEs) should be captured and reported because they can have a significant negative impact on patients and treatment adherence. However, the reporting of NSAEs in randomised controlled trials (RCTs) is limited.

There is little evidence for finding optimal antipsychotic treatment for schizophrenia, especially in paediatrics. To evaluate the performance and clinical benefit of several prediction methods for 1-year treatment continuation of antipsychotics.

Behavioural and cognitive interventions remain credible approaches in addressing loneliness and depression. There was a need to rapidly generate and assimilate trial-based data during COVID-19.

A network meta-analysis (NMA) usually assesses multiple outcomes across several treatment comparisons. The aims to facilitate communication of multiple outcomes from NMAs to patients and clinicians.

Despite uncertain benefits, people with personality disorder are commonly treated with antipsychotic medication.

Available prediction models of cardiovascular diseases (CVDs) may not accurately predict outcomes among individuals initiating pharmacological treatment for attention-deficit/hyperactivity disorder (ADHD).

Although mental pain is present in many mental disorders and is a predictor of suicide, it is rarely investigated in research or treated in care. A valid tool to measure it is a necessary first step towards better understanding, predicting and ultimately relieving this pain.

The COVID-19 pandemic has caused an increase in mental ill health compared with prepandemic levels. Longer-term trajectories of depression in adults during the pandemic remain unclear.

Predictors of antidepressant response in older patients with major depressive disorder (MDD) need to be confirmed before they can guide treatment.

Effective prevention of suicide requires a comprehensive understanding of risk factors.

Studies report an increased risk of self-harm or suicide in people prescribed mirtazapine compared with other antidepressants.

There is limited recent information regarding the risk of self-harm, somatic disorders and premature mortality following discharge from psychiatric hospital in young people.

Systematic reviews suggest school-based mindfulness training (SBMT) shows promise in promoting student mental health.

Because of the rapidly increasing number of randomised controlled trials (RCTs) and meta-analyses in many fields, there is an urgent need to step up from meta-analyses to higher levels of aggregation of outcomes of RCTs. Network meta-analyses and umbrella reviews allow higher levels of aggregation of RCT outcomes, but cannot adequately cover the evidence for a whole field. The 'Meta-Analytic Research Domain' (MARD) may be a new methodology to aggregate RCT data of a whole field. A MARD is a living systematic review of a research domain that cannot be covered by one PICO. For example, a MARD of psychotherapy for depression covers all RCTs comparing the effects of all types of psychotherapy to control conditions, to each other, to pharmacotherapy and combined treatment. It also covers all RCTs comparing treatment formats, the effects in different target groups, subtypes of depression and secondary outcomes. Although the time and resources needed to build a MARD are considerable, they offer many advantages, including a comprehensive and consistent overview of a research field and important meta-analytic studies that cannot be conducted with conventional methods. MARDs are a promising method to step up the aggregation of RCTs to a next level and it is highly relevant to work out the methods of this approach in a more detailed way.

Improving child and adolescent mental health requires the careful development and rigorous testing of interventions and delivery methods. This includes universal school-based mindfulness training, evaluated in the My Resilience in Adolescence (MYRIAD) trial reported in this special edition. While discovering effective interventions through randomised controlled trials is our ultimate aim, null or negative results can and should play an important role in progressing our understanding of what works. Unfortunately, alongside publication bias there can be a tendency to ignore, spin or unfairly undermine disappointing findings. This creates research waste that can increase risk and reduce benefits for future service users. We advocate several practices to help optimise learning from all trials, whatever the results: stronger intervention design reduces the likelihood of foreseeable null or negative results; an evidence-informed conceptual map of the subject area assists with understanding how results contribute to the knowledge base; mixed methods trial designs aid explanation of outcome results; various open science practices support the dispassionate analysis of data and transparent reporting of trial findings; and preparation for null or negative results helps to temper stakeholder expectations and increase understanding of why we conduct trials in the first place. To embed these practices, research funders must be willing to pay for pilot studies and 'thicker' trials, and publishers should judge trials according to their conduct and not their outcome. MYRIAD is an exemplar of how to design, conduct and report a trial to optimise learning, with important implications for practice.

Preventing mental health problems in early adolescence is a priority. School-based mindfulness training (SBMT) is an approach with mixed evidence.

Previous research suggests that mindfulness training (MT) appears effective at improving mental health in young people. MT is proposed to work through improving executive control in affectively laden contexts. However, it is unclear whether MT improves such control in young people. MT appears to mitigate mental health difficulties during periods of stress, but any mitigating effects against COVID-related difficulties remain unexamined.

Education is broader than academic teaching. It includes teaching students social-emotional skills both directly and indirectly through a positive school climate.

Universal school programmes aimed at the prevention of depression and other common mental health problems in adolescents are attractive because they are less stigmatising than targeted interventions, have a high uptake and may shift the 'normal distribution' of mental health problems in the positive direction. Research up to now shows small effects of these interventions, but even small effects may have a large impact because of the large number of people receiving these interventions. However, such small effects may also be related to the modest quality of the trials in this area. This means that current research has no clear indication whether universal prevention has a large public health impact or no impact at all. The MYRIAD trial is a large, fully powered, high-quality study showing that universal prevention probably is not effective, although it it is possible that other interventions or approaches do have significant effects. We should seriously consider to move to other approaches to reduce the disease burden of depression in adolescents. Indirect approaches seem to be a feasible and promising alternative approach to prevention and increase the uptake of effective interventions.

Mindfulness-based programmes (MBPs) are an increasingly popular approach to improving mental health in young people. Our previous meta-analysis suggested that MBPs show promising effectiveness, but highlighted a lack of high-quality, adequately powered randomised controlled trials (RCTs). This updated meta-analysis assesses the-state-of the-art of MBPs for young people in light of new studies. It explores MBP's effectiveness in active vs passive controls; selective versus universal interventions; and studies that included follow-up.

The association between serum folate deficiency and the risk of dementia in old age is unclear, perhaps owing to small sample sizes, the competing risk of mortality or reverse causation.

Advances in genetics and digital phenotyping in psychiatry have given rise to testing services targeting young people, which claim to predict psychiatric outcomes before difficulties emerge. These services raise several ethical challenges surrounding data sharing and information privacy.