The COVID-19 vaccine may protect against SARS-CoV-2’s adverse effects on mental health, according to an analysis of more than 18.6 million adults by a team of researchers in the U.K.

You’re not alone if you’ve experienced new or worsening mental illness after recovering from COVID. While the coronavirus’s long-term consequences on mental health remain a mystery, in the four years since the pandemic’s onset, researchers worldwide have already documented a link between infection and mental health deterioration.

Now scientists in the U.K. have uncovered a new piece of the puzzle: COVID vaccination may mitigate the virus’s adverse effects on mental health. The team, including researchers from the universities of Bristol, Cambridge, Oxford, and Swansea, as well as University College London, showed higher rates of mental illnesses among unvaccinated people, up to a year after severe COVID infection. Their findings were published Wednesday in JAMA Psychiatry.

“Our findings have important implications for public health and mental health service provision, as serious mental illnesses are associated with more intensive health care needs and longer-term health and other adverse effects,” Venexia Walker, PhD, a senior research fellow in epidemiology at Bristol Medical School and one of the study’s lead authors, said in a news release. “Our results highlight the importance of 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.”

The observational study assessed the medical records of more than 18.6 million adults ages 18 to 110 (50% female; median age 49) who were registered with a general practitioner in England. In this first cohort, which centered on the pandemic’s early days before a vaccine was available, about 5% of patients had been diagnosed with COVID. Two other cohorts represented the vaccination era from June through December 2021:

Vaccinated: 14 million people

Female: 52%

Median age: 53

COVID diagnosis: 6%

Unvaccinated: 3.2 million people

Female: 42%

Median age: 35

COVID diagnosis: 5%

In each of the three cohorts, researchers compared incidence of the following mental illnesses before and after a confirmed COVID diagnosis:

Addiction

Depression

Eating disorders

General anxiety

Posttraumatic stress disorder

Self-harm

Serious mental illness (including bipolar disorder and schizophrenia)

Suicide

Compared to before or without COVID, the prevalence of most of these conditions increased one to four weeks following COVID diagnosis. This trend primarily applied to severe infections that had required hospitalization and among unvaccinated people, incidence remained elevated for up to a year.

Mental illness incidence increased slightly in COVID patients who endured milder infection. Depression rates, for example, spiked 16-fold among hospitalized patients but did so by just 1.2 times among nonhospitalized patients. While no vaccine is 100% effective, COVID immunization is intended to prevent severe illness and death. Researchers noted that the vaccinated cohort showed little variation in depression prevalence before/without or after nonhospitalized infection.

The link between COVID and mental illness didn’t change significantly between racial and ethnic groups. It did, however, vary by age and biological sex. For instance, this association was stronger among men and older age groups.

Despite boasting a large sample size, the study has its limitations. The millions of participants hailed from a single nation, and the vast majority were white. Researchers also stressed that they analyzed only confirmed infections recorded in electronic health records, meaning COVID-positive individuals who hadn’t sought medical care weren’t included. In addition, researchers couldn’t rule out that viruses besides SARS-CoV-2 hadn’t contributed to the mental illnesses studied.

“We have already identified associations of COVID-19 with cardiovascular disease, diabetes, and now mental illnesses,” Jonathan Sterne, PhD, study coauthor and professor of medical statistics and epidemiology at Bristol Medical School, said in the news release. “We are continuing to explore the consequences of COVID-19 with ongoing projects looking at associations of COVID-19 with renal, autoimmune, and neurodegenerative conditions.”

When will the new COVID vaccines be available?

Updated 2024–2025 COVID vaccines likely will be available in the early fall. Vaccines manufactured by Pfizer, Moderna, and Novavax will arrive “later this year,” the Centers for Disease Control and Prevention (CDC) announced in June. Last year’s version launched in mid-September.

When the new vaccines are available, the CDC recommends everyone aged 6 months and older get a dose to shield themselves from the latest Omicron subvariants. People with compromised immune systems and those 65 and older may be eligible for additional doses.

“Our top recommendation for protecting yourself and your loved ones from respiratory illness is to get vaccinated,” CDC Director Dr. Mandy Cohen said in a June news release. “Make a plan now for you and your family to get both updated flu and COVID vaccines this fall, ahead of the respiratory virus season.”