Excerpts from the editorial:

>So, what did we learn? The authors found no evidence in the general (not high risk) population of changes in general mental health, except for a slight deterioration in symptoms of depression. The word “slight” is important here. Sun and colleagues used a metric called the standardised mean difference, or SMD, and found a deterioration in depression symptoms of 0.12 SMD after the onset of the pandemic. Formally, this means a deterioration of 0.12 standard deviations. Cohen, who invented the metric, developed it for randomised trials and estimated that SMD values less than 0.2 indicated a minimal effect, 0.2-0.5 a small effect, 0.5-0.8 a moderate effect, and 0.8 or more a large effect.2 This may be too simplistic, however, and values between 0.24 and 0.5 have generally been suggested to correspond to a minimal clinically relevant difference for trials in people with depression.3 Whether these cut-offs can be directly applied to general population studies, such as those in Sun and colleagues’ systematic review, is not yet clear.

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>Some individuals or subgroups might experience larger deteriorations than the population mean. The authors identify women as a vulnerable subgroup for depression, anxiety, and general mental health, although deteriorations were still minimal or small on average. Media attention has often focused on the pandemic’s particular impact on young people, but this is not born out by the present study: parameters of anxiety, depression, and general mental health did not deteriorate significantly in young adults, adolescents, or children. Future updates of this systematic review, which the authors will post online as more evidence accrues (https://www.depressd.ca/covid-19-mental-health), could usefully examine other subgroups, such as socially marginalised individuals.

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>Finally, while the present study clearly shows that we need not be overly concerned about the general population’s mental health in relation to the covid-19 pandemic, reported prevalence rates of mental health symptoms, especially among adolescents, are still concerningly high.101112 Pandemic or not, there is a strong need to provide preventive mental health interventions for those most at risk of poor mental health outcomes.

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Please note that the editorial provided a link to the actual research (Comparison of mental health symptoms before and during the COVID-19 pandemic) and a link to a stakeholder's opinion (A patient's perspective on mental health and the pandemic). All links are free full-text access.