Mental illnesses linked in new study to higher risk of COVID-19 breakthrough infections

A new study suggests that individuals with a history of certain mental illnesses may be at a higher risk of COVID-19 breakthrough infections after being vaccinated.

Researcher Kristen Nishimi said that could be because patients with some psychiatric disorders can have a "decreased immunological response to vaccine."

And the findings show individuals with psychiatric disorders should be one of the groups that get prioritized for booster vaccines and other preventative efforts, researchers said.

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The study, out of the University of California San Francisco, looked at data from 263,697 fully vaccinated patients who accessed health care from the U.S. Departments of Veterans Affairs between February 2020 and November 2021. They published their findings last Thursday in the journal JAMA Network Open.

Of the cohort, 135,481 patients (51.4 per cent) were diagnosed with at least one psychiatric condition such as substance abuse, psychotic disorders, bipolar disorder, adjustment disorder and anxiety. In addition, 39,109 patients (14.8 per cent) developed a breakthrough infection.

The researchers found that for patients under 65, the risk of developing a COVID-19 breakthrough infection was up to 11 per cent higher for those who had been diagnosed with a psychiatric condition. And for patients 65 or over, having a psychiatric history represented up to a 24 per cent higher risk of COVID-19.

Given the higher incidence of breakthrough infections among older patients, Nishimi said the lower immunological response to vaccine linked to some psychiatric disorders "may be more substantial in older adults."

"(Older patients) may require more frequent in-person care, which could increase their interactions with the health-care system," Nishimi said in a news release published Thursday.

For both groups, the risk factors were also adjusted for variables such as age, race, vaccine type, underlying conditions

“Our research suggests that increased breakthrough infections in people with psychiatric disorders cannot be entirely explained by socio-demographic factors or pre-existing conditions,” said senior author Aoife O'Donovan in the news release. "Mental health is important to consider in conjunction with other risk factors."

The risk factors varied based on the type of condition. For patients 65 and over, the study found that the risk of having a breakthrough infection was 24 per cent higher among people with a history of substance abuse, 23 per cent higher for those with psychotic disorder, 16 per cent higher for bipolar disorder, 14 per cent for adjustment disorder and 12 per cent for anxiety.

O'Donovan says a possible explanation may be due to waning immunity exacerbated by these mental health conditions.

“It’s possible that immunity following vaccination wanes more quickly or more strongly for people with psychiatric disorders and/or they could have less protection to newer variants,” she said.