In a recent study published in JAMA Psychiatry, a team of scientists from the United Kingdom (U.K.) investigated whether coronavirus disease 2019 (COVID-19) was associated with mental health illnesses and whether the association was modified based on COVID-19 vaccination status among the general population, as well as among patients who were hospitalized due to the disease.

​​​​​​​Study: COVID-19 and Mental Illnesses in Vaccinated and Unvaccinated People​​​​​​​. Image Credit: Viacheslav Lopatin/Shutterstock.com

Background

Numerous studies on hospitalized COVID-19 patients as well as non-hospitalized individuals who experienced milder forms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection have shown that COVID-19 is associated with the subsequent development of mental health illnesses.

These include mental health impairments such as depression and anxiety, as well as more severe forms such as psychotic disorders.

While microvascular alterations and persistent inflammation due to SARS-CoV-2 infection are some of the potential physiological mechanisms linked to mental health illnesses after COVID-19, psychosocial causes such as anxiety about the disease and the outcomes post-COVID-19 have also been implicated.

Furthermore, although the rapid development of COVID-19 vaccines was instrumental in limiting the transmission and morbidity of SARS-CoV-2 infections, the long-term implications of these rapidly developed vaccines on other post-COVID-19 outcomes, including mental health issues, remain unclear.

About the study

In the present study, the researchers used electronic health records of over 18 million individuals in the U.K. to examine associations between COVID-19 diagnoses and the subsequent development of mental health illnesses before the availability of the vaccine and in vaccinated and unvaccinated individuals after COVID-19 vaccine rollouts.

The associations were also examined separately based on sex, age, disease severity, ethnicity, previous SARS-CoV-2 infections, and history of mental health illnesses.

The mental health illness outcomes examined in the study were depression, generalized anxiety disorders, addiction, eating disorders, self-harm, and post-traumatic stress disorder, as well as serious illnesses such as bipolar disorder, schizoaffective disorder, schizophrenia, and psychotic depression.

Covariates such as sex, age, ethnicity, smoking status, comorbidities, deprivation, employment in health care, and residence in a care home were included as potential cofounders. Three cohorts were included in the study, with the follow-up for the pre-vaccine cohort stretching from early January 2020 to mid-December 2021.

Since the vaccine became available for all adults on June 18^th, 2021, the follow-up for the vaccinated cohort began around then, or two weeks after the second dose of the COVID-19 vaccine, and ended in mid-December 2021, which was the end of the study. For the unvaccinated cohort, the follow-up began 12 weeks after the vaccine became available.

COVID-19 diagnoses were confirmed based on laboratory tests, irrespective of the manifestation of symptoms.

The follow-up period for the pre-vaccine cohort overlapped with the period of circulation of the wild-type and Alpha variants of SARS-CoV-2, while the follow-ups for the vaccinated and unvaccinated cohorts were during the period of circulation of the Delta variant.

Confirmed diagnoses of COVID-19 were the exposure in the study, and the measured outcomes were comparisons of adjusted hazard ratios for the incidence of various mental health illnesses before and after the availability of the COVID-19 vaccine and between unvaccinated and vaccinated individuals.

Results

The study found that the incidence of mental health illnesses was higher for close to a year after COVID-19 among individuals who were not vaccinated against SARS-CoV-2 infections.

The findings showed that the mental health illness incidence rates were significantly higher in the four weeks following the onset of the COVID-19 pandemic as compared to before the pandemic.

However, the incidence rates were relatively lower among the vaccinated cohort. Furthermore, the incidence rates for mental health illnesses remained higher for close to seven months in individuals who got COVID-19 before the vaccinations became available, especially among those hospitalized for acute SARS-CoV-2 infections.

The subgroup analyses showed that the association between COVID-19 and the incidence of mental health illnesses was stronger among men, older adults, and those with a history of mental health illnesses. However, the association did not vary significantly between ethnic groups.

While COVID-19 vaccines were found to mitigate the impact of SARS-CoV-2 infections on subsequent mental health status, the study showed that a history of mental health illnesses influenced vaccine uptake.

This finding highlighted the importance of actively encouraging individuals with existing mental health illnesses to get vaccinated.

The high incidence of mental health illnesses associated with COVID-19 before the availability of the vaccine also potentially reflects the greater levels of uncertainty and concern surrounding COVID-19 outcomes and the effectiveness of treatment options in the early stages of the pandemic.

Conclusions

Overall, the study found that the COVID-19 vaccine mitigated the incidence of mental health illnesses, and unvaccinated individuals were at a higher risk of developing mental health difficulties after COVID-19.

The association was stronger among men and older adults, as well as among people with a history of mental health issues, highlighting the need for encouraging vaccine uptake.