Psychological distress among people with probable COVID-19 infection: analysis of the UK Household Longitudinal Study

Summary Studies exploring the longer-term effects of experiencing coronavirus disease-2019 (COVID-19) on mental health are lacking. We explored the relationship between reporting probable COVID-19 symptoms in April 2020 and psychological distress (measured using the General Health Questionnaire) 1, 2, 3, 5 and 7 months later. Data were taken from the UK Household Longitudinal Study, a nationally representative household panel survey of UK adults. Elevated levels of psychological distress were found up to 7 months after probable COVID-19, compared with participants with no likely infection. Associations were stronger among younger age groups and men. Further research into the psychological sequalae of COVID-19 is urgently needed.


Background
Considerable concerns exist about the longer-term effects of experiencing coronavirus disease-2019 (COVID-19). 1 However, population-based data remain rare, with the majority of COVID-19 research focused on severe adverse physical consequences of acute disease. There is growing evidence that a substantial number of people experience persisting symptoms such as fatigue and chest pain months after infection. 2 Although the mental health consequences of societal changes during the pandemic (including lockdown) have been extensively studied, 3,4 research on the impact of COVID-19 infection on mental health is limited.
Research from previous coronavirus outbreaks demonstrates potential for psychiatric consequences of infection. 5 An initial study using administrative data from the USA demonstrated that COVID-19 infection was associated with an increased incidence of psychiatric diagnoses (particularly anxiety and insomnia) in the following 14-90 days. 6 Studies have also demonstrated that COVID-19 survivors who received emergency department evaluation in Milan had high levels of depression and anxiety 1 month following discharge 7 and COVID-19 patients in Chongqing, China had more symptoms of stress, anxiety and depression compared with healthy and psychiatric patient controls. 8 However, most existing studies have been limited by small, non-representative samples and those based on electronic health records may not capture individuals with more minor acute COVID-19 symptoms or those with less severe psychological problems that do not present to health services. Changes in healthcare-seeking and treatment may lead to substantial potential bias in the context of a pandemic, where disruptions to health systems have been widespread. Data from surveys may therefore be better placed to capture the impact on mental health and need for intervention.

Aims
To explore the relationship between COVID-19 infection and mental health in the UK context, we assessed associations between experiencing COVID-19 symptoms and changes in psychological distress in a representative longitudinal survey of adults.

Method
The UK Household Longitudinal Study (also referred to as Understanding Society) is a nationally representative longitudinal household panel survey, based on a clustered stratified probability sample of UK households, described in detail previously. 9 All adults (aged ≥16 years) in chosen households are invited to participate. Data collection for each wave usually takes place over 24 months, with participants re-interviewed every year by online, face-to-face or telephone survey.
We used pre-pandemic data from wave 9 (2017-19), which achieved a household response rate of over 80%. 10 In response to the COVID-19 pandemic, additional waves of data were collected in 2020 via online survey during April (24 to 30 April), May (27 May to 2 June), June (25 June to 1 July), July (24 to 31 July), September (24 September to 1 October) and November (24 November to 1 December). 11 The response rate for the first COVID wave was 48.6% of those who took part at wave 9. 12 Psychological distress was measured at each wave (pre-pandemic in 2017-19 and during the pandemic at each wave as above) via the General Health Questionnaire 12-item instrument (GHQ-12). 13 GHQ-12 assesses psychological distress and respondents reporting a score of 4 or more are likely experiencing symptoms to a clinically significant level. 3 Self-reported symptoms of cough, fever and anosmia allowed identification of individuals with probable COVID-19 infection in April 2020 (see Supplementary Material available at https://doi.org/10.1192/bjo.2021.63).
Of 42 people reporting hospital admission for COVID-19 in April 2020, 34 were classified as probable COVID-19 according to our definition. We assessed associations between probable COVID-19 infection and psychological distress at 1, 2, 3, 5 and 7 months later using logistic regression, with models adjusted to account for pre-pandemic psychological distress (GHQ score) and other covariates (gender, age, ethnicity and long-standing illness or disability). We also conducted subgroup analyses by age group (under 45, 45-64, ≥65 years) and gender (men, women) to investigate potential effect modification by demographic characteristics associated with COVID-19.
Analyses used inverse probability weights to adjust for nonresponse and standard errors were adjusted for the complex survey design. Missing data were excluded from analyses, but if participants were missing pre-pandemic wave 9 data responses from wave 10 were used if available. Statistical analyses were performed in Stata/MP 15.1.
The University of Essex Ethics Committee approved all data collection for the Understanding Society main survey and COVID waves, which were performed in accordance with the Declaration of Helsinki. All survey participants provided fully informed consent. No additional ethical approval was necessary for this secondary data analysis.
Subgroup analyses demonstrated stronger associations in men (OR = 1.52 in May, 95% CI 1.05-2.20) and younger adults (OR = 1.51 in May, 95% CI 1.07-2.13), with some differences in the strength of associations at different time points.

Main findings
Our study suggests that COVID-19 infection could lead to an increase in clinically significant psychological distress that persists months after infection and is additional to the mental health impact of societal changes during the pandemic. Younger people and men with probable COVID-19 infection were more likely to report clinical levels of psychological distress compared with older age groups and women. There were some differences in the strength of associations over time that require further investigation to understand whether factors, such as lockdown restrictions, modify the association between COVID-19 symptoms and mental health.

Strengths and limitations
Our findings add to the growing evidence that COVID-19 infection may have a direct impact on mental health 8,14 that persists months after initial symptoms. 6,7 Study strengths include the longitudinal data over multiple points of follow-up during the pandemic, the representative UK sample and accounting for pre-pandemic mental health to limit reverse causation. Important limitations include the ascertainment of COVID-19 infection, based on self-report only (not confirmed by a laboratory test) and the classification of probable COVID-19 infection at only one time point. However, misclassification may be more likely to result in underestimation of any underlying association. Further research based on confirmed infection is required, as is research that takes into account the fluctuating nature of symptoms (i.e. 'long-COVID') and research that compares the impact of COVID with that of other illnesses, such as pneumonia.
The self-reported nature of the exposure and outcome measures also means we cannot rule out the possibility of reverse causation in which poor mental health influences the reporting of COVID-19 symptoms. Triangulation of survey and administrative data (such as primary care and psychotropic prescribing records) would be helpful to disentangle the discrepancy between likely clinical need and service use and help to overcome the limitations of self-reported data.

Implications
The potential adverse impact of COVID-19 infection on mental health reinforces the benefits of minimising COVID-19 infection among the general population, not only in those at greatest risk of mortality. When considered alongside the mental health impact generated by mitigation measures, there is potential for a high demand for mental health services resulting from the pandemic. Further research to examine the longer-term psychological sequelae