The impact of COVID-19 on mental health has been a topic of emerging concern. A new large-scale study involving data from around 18 million adults adds more evidence to the link, as researchers noticed a higher incidence of mental illness following severe COVID infection in unvaccinated individuals.

The study published in Jama Psychiatry investigated the relationship between COVID-19 vaccination status and the incidence of mental illnesses such as depression, serious mental illness, general anxiety, post-traumatic stress disorder, eating disorders, addiction, self-harm, and suicide.

The study examined the health records of 18,648,606 adults aged 18 to 110 years. Of these, 1,012,335 had a confirmed COVID-19 diagnosis. Among the vaccinated cohort of 14,035,286 adults, 866,469 had a confirmed COVID-19 diagnosis. In the unvaccinated cohort, which included 3,242,215 adults, 149,745 had a confirmed COVID-19 diagnosis.

The study noted that the incidence of most mental illnesses was elevated during weeks 1 through 4 after COVID-19 diagnosis, compared with before or without COVID-19. Elevated incidence of mental illnesses after COVID-19 infection was mainly observed among cases where there were hospitalizations, and the risk remained high for up to a year following severe COVID-19 in unvaccinated individuals.

When comparing the incidence of depression between hospitalized and non-hospitalized COVID-19 cases, researchers found that depression was 16.3 times more common among those who were hospitalized. In contrast, it was 1.22 times higher in individuals who were not hospitalized. These comparisons are made against the depression rates of individuals who did not have COVID-19 or the rates before the infection.

However, in those who took COVID shots, the incidence of depression in non-hospitalized situations was similar to that of their risk before or without COVID-19.

"The findings add to a growing body of evidence highlighting the higher risk of mental illnesses following COVID-19 diagnosis, and the benefits of vaccination in mitigating this risk, with stronger associations found in relation to more severe COVID-19 disease, and longer-term associations relating mainly to new-onset mental illnesses," the news release stated.

"Our results highlight the importance COVID-19 vaccination in the general population and particularly among those with mental illnesses, who may be at higher risk of both SARS-CoV-2 infection and adverse outcomes following COVID-19," said Dr. Venexia Walker, the study's lead author.

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