According to a study published in The BMJ, mental health in the general population has not altered much throughout the covid-19 pandemic compared to pre-pandemic levels.

Some specific groups, particularly women, appear to have been more negatively affected, but changes have been minimal to small, say the researchers. Many studies and media reports suggest that covid-19 has led to widespread decline in mental health, but inconsistencies in study quality and misinterpretation of cross-sectional data may have led to misleading results.

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To address this, researchers reviewed 137 studies that compared general mental health, anxiety and depression symptoms in populations during the covid-19 pandemic (from 1 January 2020 or later) with pre-covid assessments (1 January 2018 to 31 December 2019).

Studies had to report data from groups comprising at least 90% of the same participants between pre-pandemic and pandemic periods or to use statistical methods to account for missing data. Most of the eligible studies were from high or upper middle income countries and were thoroughly assessed for bias before being included in the analysis.

Differences between groups were expressed as standardised mean differences (SMD). Generally, an SMD of less than 0.2 indicates 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.

Among general population studies, no changes were found for general mental health or anxiety symptoms, but depression symptoms worsened minimally (SMD change 0.12).

Among specific groups, women or female participants were the only group that experienced a worsening of symptoms across all outcomes; all by small amounts (SMD changes 0.20 to 0.22). This is consistent with evidence that women and female members of society have experienced a disproportionately greater burden from the pandemic, note the researchers.

Depression symptoms worsened by minimal to small amounts for older adults, university students, and people who self-identified as belonging to a sexual or gender minority group, but not for other groups.

General mental health and anxiety symptoms were shown to worsen for parents, although the researchers stress that these results were based on small numbers of studies and participants.

In contrast, general mental health and depression symptoms were shown to improve for people with pre-existing mental health conditions. But, again, the researchers stress that these results were based on only two studies and improvement was negligible (SMD change 0.05).

No other subgroup experienced significant changes across all outcomes, including young people.

This was a well designed review based on a thorough literature search, but the researchers acknowledge that differences in study design, a high risk of bias in many studies, and a lack of evidence from lower income countries and children may have had an influence, and they suggest caution is needed in interpreting their results.

“Across population groups, results suggest that, rather than a mental health crisis, at a population level there has been a high level of resilience during covid-19, and changes in general mental health, anxiety symptoms, and depression symptoms have been minimal to small with no changes detected in most analyses,” they write.

Nevertheless, they say the pandemic has affected the lives of many people, and urge governments to “continue to ensure that mental health supports are available and respond to population needs.”

While this 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, say researchers from Denmark in a linked editorial.

This review does not tell us why any deteriorations occurred, or whether these deteriorations might have occurred even without the pandemic, signifying an underlying, but not covid-19 related, pan-societal problem, they write. Further research is required to help answer these important questions.

“Pandemic or not, there is a strong need to provide preventive mental health interventions for those most at risk of poor mental health outcomes,” they conclude.