Some have called it a “tsunami”, others a “mental health pandemic” – but Covid-19 might not have had such a significant impact on the general population, according to a new study that has qualified the impact of the pandemic on mental health worldwide.

Studies, surveys, testimonies, and health authorities around the world have been unanimous for nearly three years that the pandemic has considerably affected people’s mental health. This has led to increased efforts in prevention, and tailored treatments to limit the consequences of disorders linked to stress, anxiety and depression.

Now, a study conducted by researchers at McGill University in Montreal, Canada, contradicts – if not qualifies – previous research on the subject, suggesting that the pandemic might not have had such a detrimental impact on mental health after all.

In March last year, the World Health Organization reported a 25% increase in the prevalence of anxiety and depression worldwide triggered by Covid-19. But the Canadian researchers, who have conducted the most recent work on the subject, are now suggesting that “inconsistencies in study quality and misinterpretation of cross-sectional data may have led to misleading results”.

This led them to review as many as 94,411 titles and abstracts, including 137 studies from 134 cohorts, to compare mental health symptoms before and during the pandemic.

Published in the British Medical Journal, this research is based specifically on a comparison of mental health and anxiety/depression symptoms in the general population as of Jan 1, 2020, compared with a period from Jan 1, 2018 to Dec 31, 2019.

All studies analysed were required to have at least 90% identical participants for the time periods examined, while the impact of Covid-19 on mental health was expressed as standardised mean differences (SMD), with less than 0.2 considered a “minimal effect” and more than 0.8 considered a “large effect”.

According to the results, “no changes were found for general mental health or anxiety symptoms”. But this was not the case for depression symptoms, which “worsened minimally” with the pandemic.

The researchers report an SMD of 0.12, and thus a “minimal effect” for these disorders.

“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.

“Changes in general mental health, anxiety and depression symptoms have been minimal to small, with no changes detected in most analyses,” the authors write.

Women affected more significantly

However, the researchers point out disparities between the different groups of the general population, with women having suffered more during the pandemic.

In any case, they experienced a more significant worsening of symptoms of anxiety, depression and general mental health than the rest of the population, with SMD of 0.20 to 0.22, an effect considered “small”.

“This is consistent with evidence that women and female members of society have experienced a disproportionately greater burden from the pandemic,” the researchers note.

And they were not the only ones: the elderly, students, and people who identify as belonging to a sexual or gender minority also appear to have experienced a worsening of depressive symptoms by “minimal to small” amounts, the research points out.

Parents, too, have reportedly seen their mental health decline, but the researchers specified that, in this case, the data is based on a limited number of studies and participants.

The bigger picture

As surprising as these results may be, they should be treated with caution, if only because they exclude certain groups of the general population. Based on an extensive meta-analysis, the study authors admit it does not include enough data from low-income countries and children.

The authors believe that caution should be exercised in interpreting these results, bearing in mind that the pandemic “affected the lives of many people”, and call on the relevant authorities to “continue to ensure that mental health supports are available and respond to population needs”.

Speaking to the “Guardian” about the McGill study findings, Dr Gemma Knowles from the Centre for Society and Mental Health at King’s College London notes that this research potentially shows that some people’s mental health worsened during the pandemic while others’ improved, explaining the lack of an overall increase in symptoms.

She strikes a more cautionary tone, suggesting that the study “risks obscuring important effects among the most affected and disadvantaged groups and, from that, obscuring possible widening of inequalities in mental distress that occurred because of the pandemic”.

On its part, the WHO has been warning governments for the past three years about the effect of the pandemic on populations, reiterating as recently as in June that “the impact of Covid-19 on mental health cannot be made light of”.

The organisation recalls in particular the impact of prolonged school closures and social isolation on young people, not to mention the risk of family stress or abuse linked to lockdowns.

Then there’s the increased stress and violence suffered by women, and the “millions of people who have fallen below the poverty line” due to the pandemic. These are all factors that can affect the mental health of these specific groups.

And this is something that, despite their findings, the McGill researchers do not overlook. “Pandemic or not, there is a strong need to provide preventive interventions for those most at risk of poor mental health outcomes,” they conclude.