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23 papers
Our findings suggest that geographic location plays a limited role in the reasons for the large variability of ADHD/HD prevalence estimates worldwide. Instead, this variability seems to be explained primarily by the methodological characteristics of studies.
The authors pooled results from 61 cross-sectional studies to estimate how common ADHD is in children and adolescents worldwide. They found a pooled prevalence of 7.6% (95% CI 6.1–9.4%) in children aged 3–12 (from 96,907 children) and 5.6% (95% CI 4.8–7%) in adolescents aged 12–18. Prevalence estimates varied by age…
The authors combined results from 42 studies of people in prison to estimate how common ADHD is in those groups. Using formal diagnostic interviews, the overall ADHD rate was about 25.5%. Reported rates were higher when studies used screening tools or when adults recalled childhood ADHD. The review found much…
This review looked at studies that measured cortisol (a stress hormone) after people visited forests, a practice called forest bathing or shinrin-yoku. The authors found that people in forest groups had lower salivary cortisol than people in urban groups, both before and after the visits. The reviewers say the change…
This 2022 systematic review and meta-analysis pooled data from 223 studies to see if voluntary slow breathing (VSB) changes heart rate variability that reflects parasympathetic (vagal) control of the heart. The authors found that VSB increased vagally-mediated heart rate variability during breathing sessions, right after a single session, and after…
This systematic review looked at 83 published reports on ketamine for mental health and substance use disorders. It found strong evidence that ketamine can produce rapid antidepressant and anti‑suicidal effects, but these benefits tend to be short‑lived. Evidence for other conditions was weaker but often showed similar short-term effects. Many…
This meta-analysis looked at randomized trials to see if deliberate breathing practices (breathwork) reduce self-reported stress. Across 12 trials with 785 adults, breathwork was linked with a small-to-medium drop in stress compared with non-breathwork controls (g = -0.35). Similar small-to-medium effects were seen for anxiety and depression. Most included studies…
This meta-analysis combined 20 randomized clinical trials up to February 22, 2019, and found that a single dose of ketamine produced rapid antidepressant effects that were strongest at 24 hours and that these effects were still detectable up to 7 days. The analysis also found that repeated ketamine doses helped…
This large review combined 441 randomized trials with 33,881 patients to measure how many people show a clear response to psychotherapy across eight mental disorders. Response was defined as at least a 50% reduction in symptoms from before to after treatment. Pooled response rates were modest (for example, about 42%…
This review combined 17 studies of deep brain stimulation (DBS) for people with treatment-resistant depression. Across studies, about 56% of patients showed a clinical response and 35% reached remission, while 14% later had recurrence. Adverse events were common (about 67%), and the two randomized trials did not show a clear,…
This meta-analysis combined 14 observational studies and found that anaemia was associated with higher odds of adult depression (pooled estimate 1.43; 95% CI 1.23 to 1.65). The analysis included 10,764 cases of depression from studies with average ages between 38.4 and 75.0 years. The authors reported moderate differences across studies,…
