Table 1.

The impact of COVID-19 on stress resilience and mental health in the general population.

Study	Population	Time period/ wave	Study type and sample size	Objective(s)/Main outcomes	Inclusion criteria	Main findings/Summary
McGinty et al., 2020	US Adults aged 18 years or older	April 7–13 2020	Cross-sectional,N = 1468	Psychological distress and loneliness among US adults in April 2020 (Johns Hopkins COVID-19 Civic Life and Public Health Survey) compared to the 2018 National Health Interview Survey (NHIS)	Unknown	3.9% of US adults reported psychological distress in 2018 compared to 13.6% in April 2020. In April 2020, 13.8% of US adults reported that they always or often felt lonely.
Gloster et al., 2020	Adults aged 18 years or older from 78 different countries	April 7 - June 7 2020,	Cross-sectional, N = 9565	The impact of COVID-19 pandemic associated lockdowns on mental health outcomes (stress (PSS), depression (MSBS) positive/negative affect (PANAS), wellbeing (MHC-SF))	Being at least 18 years of age and being able to read one of the 18 languages (English, Greek, German, French, Spanish, Turkish, Dutch, Latvian, Italian, Portuguese, Finnish, Slovenian, Polish, Romanian, Hong Kong, Hungarian, Montenegrin, & Persian)	The highest level of mental health difficulties were found in approximately 10% of the population. The pandemic was experienced moderately and highly stressful for 55.9% and 11% respectively. Symptoms of depression were high, with 25% reporting lack of reinforcement, 33% indicating boredom and nearly 50% indicating having wasted a lot of time.
Breslau et al., 2021	US adults aged 20 years or older	Two waves: T1 (February 2019; prior to pandemic) and T2 (May 2020; during pandemic)	Longitudinal, N = 2555	The impact of the COVID-19 pandemic by comparing psychological distress (Kessler-6) experienced during the pandemic with the highest level of distress respondents had experienced during a 12-month period prior to the pandemic	Unknown	In 12.8%, an increase in psychological distress was found during COVID-19 (T2) relative to the highest level of distress before COVID-19 (T1) (95% CI 9.9%–15.7%).The experience of severe distress before at T1 was a strong predictor for the experience of severe stress at T2..
Pierce et al., 2020	UK people aged 16 years or older	April 23–30 2020; secondary analysis of the UK Household Longitudinal Study (UKHLS))	Longitudinal cohort, N = 17,452 (8.8% aged 16–24 years, 11.2% 25–34 years, 16.0% 35–44 years, 20.1% 45–54 years, 28.9% 55–69 years, 15.1% ≥ 70 years, 58.2% female, 80.4% white British, 4.5% non-white British, 1.6% mixed, 7.3% Asian, 2.2% black, 0.5% other ethnicity, 3.4% ethnicity missing)	Changes in adult mental health in the UK population before (using data from UKHLS) and during the lockdown.	Participation in either of the two most recent UKHLS data collections (Waves 8 or 9), being 16 years or older	The prevalence of clinically significant levels of mental distress was 27.3% (95% CI 26.3–28.2) in April 2020, compared to 18.9% (95% CI 17.8–20.0) in 2018–19. This increase in mental distress was higher than expected, given previous annual trends and particularly found in young people and in women.
Pierce et al., 2021	UK people aged 16 years or older	Late April – early October 2020), secondary analysis of the UK Household Longitudinal Study (UKHLS)	Longitudinal cohort, N = 19,763 (58.1% female)	Mental health trajectories during the COVID-19 pandemic and predictors of deterioration	Participation in either of the two most recent UKHLS data collections (Waves 8 or 9), being 16 years or older	Across the first 6 months of the COVID-19 pandemic up to October 2020, the mental health of most UK adults remained resilient (76.8%) or returned to pre-pandemic levels. (12.0%). For 4.1%there was an initial worsening in mental health that was sustained with highly elevated scores and 7.0% had little initial acute deterioration in their mental health, but reported a steady and sustained decline in mental health over time.
Ettman et al., 2020	US adults aged 18 or older	March 31, - April 13, 2020 (‘during COVID-19 sample’) and 2017–2018 (‘pre-COVID-19 sample’)	Cross-sectional, N = 1441 during COVID-19 (38.0% aged 18–39, 32.4% aged 40–59, 29.7% aged ≥ 60, 51.9% female) and N = 5065 pre-COVID-19 (37.8% aged 18–39, 34.2% aged 40–59, 28.0% aged ≥ 60, 51.4% female)	Prevalence of depression symptoms (PHQ-9) and factors associated with depression of US adults during vs before the COVID-19 pandemic	Being 18 years or older, speaking English, having completed an AmeriSpeak survey in the past 6 months	Prevalence of depressive symptoms was more than 3-fold higher during COVID-19 (8.5% before COVID-19 and 27.8% during COVID-19). Being exposed to more stressors and low income was associated with greater odds of depressive symptoms.
Iob, E. et al., 2020	UK adults aged 18 or older	March 21- April 2, 2020	Cohort (part of longitudinal study of adults residing in the UK (the COVID-19 Social Study), N = 51,417 (mean age 48.8 years (±16.8), 51.1% female, 12.0% of Black, Asian, and minority racial/ethnic communities)	Severity of depressive symptoms (PHQ-9) over time among individuals at high risk in the UK during the COVID-19 pandemic	Having completed at least 1 interview of the COVID-19 Social Study	UK adults with low socioeconomic position (SEP) and with psychosocial and health-related risk factors were at heightened risk of experiencing moderate and severe depressive symptoms during the COVID-19 pandemic.
Castellini et al., 2021	Italian adults aged 18–60 years	Two waves: T0 (December 1 2019, - January 15 2020,; pre-lockdown) and T1 (April 22 - May 3 2020,; 1,5 month after the declaration of lockdown)	(Longitudinal and cross-sectional, N = 671 (N = 130longitudinal, N = 541 cross-sectional; 71.4% female, mean age women 33.1 years (±14.1), mean age men 35.0 years (±14.0),	The impact of the lockdown during the pandemic on mental health (BSI) by using a longitudinal (2 waves; T0 and T1) and a cross-sectional observation (T1).	Age between 18 and 60 years, having an Italian nationality, being a resident in Tuscany	Phobic anxiety (T0: 0.26 ± 0.43; T1: 0.48 ± 0.63; p <0.001). and depressive symptoms (T0: 0.57 ± 0.48; T1: 0.73 ± 0.65; p = 0.003) increased during the lockdown as compared to a few weeks before the COVID-19 outbreak, whereas interpersonal sensitivity (T0: 0.58 ± 0.61; T1: 0.35 ± 0.61; p <0.001) and paranoid ideation (T0: 0.49 ± 0.49; T1: 0.32 ± 0.49; p <0.001) decreased.
Robinson & Daly, 2020	US adults aged 18 years or older	Six waves covering a period from March 10 -June 9 2020,	N = 7138 (34,125 observations, mean age 49.0 years (±16.5), 51.2% female)	Distress (PHQ-4) during the COVID-19 crisis and explanatory psychosocial and behavioural factors,	Being a participant in the Understanding America Study (UAS) and being 18 years or older	Personal health concerns, perceived financial risks and lifestyle changes increased and this accounted for a substantial amount of respectively 21% and 14–15% of the initial rise in distress. Reduction in personal health concerns, financial concerns, and changes in lifestyle all mediated the decrease in psychological distress.
Li, Y. et al., 2021	Chinese college students	Two waves; T1 (early phase of COVID-19 February 3–10 2020) and T2 (‘under control’ phase of COVID-19 March 24-April 3 2020,)	Longitudinal, N = 68,685 (T1 63.2% female, T2 62.6% female)	Trajectory changes of acute stress (IES-6), anxiety (GAD-7), and depressive symptoms (PHQ-9)	Being a student in one of the target universities (22 universities in Guangdong Province)	Rates of acute stress decreased over time (34.6% at T1 vs 16.4% at T2), while rates of probable depression (21.6% vs 26.3%) and anxiety (11.4% vs 14.7%) significantly increased.
Losada-Baltar et al., 2021	Spanish adults aged 18 years or older	March 21–24 2020, after the mandatory lockdown which started on March 16 2020,	Cross-sectional, N = 1310 (mean age 42.36 years (±16.20), 71.1% female)	Loneliness and distress in people exposed to COVID-19 lock-down measures and explanatory personal and relational variables	Being older than 18 year, living in Spain and experiencing the required (mandatory) situation of lock-down at home	Being female, having a younger age, having negative self-perceptions about aging, more time being exposed to news about COVID- 19, having more contact with relatives (different to those that participants co-reside with) explained 48% and 33% of the variance of distress and loneliness respectively.
Van der Velden et al., 2020	Dutch adults aged 18 years or older	Four waves; T1 (November 2018, data from the longitudinal LISS panel), T2 (March 2019, data from the longitudinal VICTIMS study), T3 (November 2019, data from the longitudinal LISS panel), T4 (March 2020, longitudinal data from the VICTIMS study)	Longitudinal, N = 3983 (T1: 50.7% female, 26.7% aged 18–45, 23.6% aged 35–49, 25.9% aged 50–64, 23.8% aged ≥ 65; T2: not reported; T3: 50.7% female, 24.9% aged 18–45, 22.9% aged 35–49, 26.1% aged 50–64, 26.1% aged ≥ 65; T4: not reported)	Prevalence of high Anxiety and Depression Symptom (ADS) levels and lack of Emotional Support (ES) before the COVID-19 outbreak during the period in which the COVID-19 pandemic developed very rapidly in the Netherlands	Being older than 18 years	No significant differences in high ADS levels were found between November 2018 (16.7%) and March 2019 (16.8%) and between November 2019 (16.9%) and March 2020 (17.0%). For lack of ES, no significant differences were found between March 2019 (20.4%) and March 2020 (19.7%), although the total scores of lack of ES were significantly lower in March 2020 (M = 10.2, SD = 3.41) than in March 2019 (M = 10.4, SD = 3.55), t(3982) = 3.50, p <0.001).
Wang, C. et al., 2020	Chinese general population (from 194 cities in China)	Two waves/surveys; T1 (January 31 - February 2, 2020), T2 (February 28 - March 1, 2020)	Longitudinal, N = 1738 with N = 333 participated in both waves (T1: 60.3% female, 53.1% aged 21.4–30.8 years; T2: 75.0% female, 46.5% aged 21.4–30.8 years)	Temporal psychological impact (IES-R) and adverse mental health status (DASS-21) during the initial outbreak and peak of COVID-19	Unknown	There were no significant longitudinal changes in mean DASS-stress (T1: M = 7.76, SD =7.74, T2: M = 7.86, SD), anxiety subscale (T1: M = 6.16, SD =6.57, T2: M = 6.16, SD =6.94) and depression scores subscale (T1: M = 6.25, SD = 7.16, T2: M = 6.38, SD =7.39) during the initial outbreak and the peak of the COVID-19 epidemic. The mean IES-R score of the second-survey respondents (M = 30.76, SD = 16.34) was significantly lower than the first-survey respondents (M = 32.98, SD = 15.42). .
The Swiss Corona Stress Study, first wave (between April 6 and 8, 2020)(prep-print: https://osf.io/jqw6a/)	Swiss general population, aged 14 years and older	April 6 - 8, 2020, starting 3 weeks after the beginning of confinement	Cross-sectional, N = 10,472 (mean age 40.3 years (± 13.6, 71% female)	The adaptation of the Swiss population to the COVID-19 outbreak and risk- and resilience factors	Living in Switzerland, being 14 years or older, having completed the survey by April 8 2020,	While 24.4% of the participants reported no change in stress levels, 49.6% of the participants reported an increase in stress levels during confinement as compared to the time before the COVID-19 pandemic.
Fancourt et al., 2021	UK adults, aged 18 years and older	March 23 (start of the first lockdown in the UK) - August 9, 2020	Prospective longitudinal observational, N = 36,520 (7.5% aged 18–29, 29.2% aged 30–45, 33.0% aged 46–59, 30.4% aged ≥ 60, 76% female)	Trajectories of anxiety and depression over the 20 weeks after lockdown was announced in England,	Having at least three repeated measures between March 23 and August 9, 2020	Anxiety and depression levels both declined across the first 20 weeks following the introduction of lockdown in England (b = –1.93, SE=0.26, p < 0.0001 for anxiety; b = –2.52, SE = 0.28, p < 0.0001 for depressive symptoms).
Gonzalez-Sanguino et al., 2020	Spanish adults	Three waves; T1 (March 21 – 29 2020), T2 (April 13 – 27 2020, during the hardest moments of the confinement with the greatest impact at the socioeconomic level) and T3 (May 21 – June 4 2020,, during initiation of de-escalation on the restrictive measures)	Longitudinal observational cohort, N = 3480 (T1: 35% aged 18–29 years, 59% aged 30–59 years, 6% aged ≥ 60 years, 75% female; T2: 29% aged 18–29 years, 64% aged 30–59 years, 7% aged ≥ 60 years, 81% female; T3: 27% aged 18–29 years, 65% aged 30–59 years, 8% aged ≥ 60 years, 81% female)	Effects of the pandemic and alarm situation on the mental health of the general population.	Being over 18 years of age, living in Spain, acceptance to participate in the successive evaluations of the study	Depressive symptoms increased significantly throughout the confinement (Z(T0-T1) = 7.06, p < 0.001, decreasing at the last assessment but not dropping to previous levels, with significant differences between the first and third evaluations (Z(T0-T2) = 4.02, p < 0.001).
Bendau, A. et al., 2020	German general population	Four waves; T1 (March 27 – April 6 2020,, during lockdown), T2 (April 24 – May 4 2020,, stepwise reduction of restrictive measures), T3 (May 15 – 35 2020) and T4 (June 6 – 15 2020, first cities introduce obligation of wearing face masks in public)	Longitudinal observational cohort, N = 2376 (N = 503 completed all four waves, mean age at T1 38.76 years (± 12.01, 76.7% female)	Symptoms of (un‐) specific anxiety and depression along different stages of the pandemic	Having an minimum age of 18 years, living in Germany, being able to complete the questionnaires in German, having participated in at least two waves of data collection	Specific COVID‐19‐related anxiety and the average daily amount of preoccupation with the pandemic decreased continuously over the four waves.
Daly & Robinson, 2020	US adults, nationally representative data from eight waves of the Understanding America Study (UAS)	Eight waves; T1 (March 10–18 2020), T2 (April 1 – 14 2020), T3 (April 14 – 28 2020), T4 (April 29 – May 12 2020,), T5 (Mat 13 – 26 2020), T6 (May 27 – June 9 2020,), T7 (June 10 – 23 2020), T8 (June 24 – July 20 2020,)	Longitudinal observational cohort, N = 7319 (22.8% aged 18–34 years, 29.6% aged 35–49 years, 26.9% aged 50–64 years, 20.7% ≥ 65 years, 51.3% female)	Psychological distress following the emergence of the COVID-19 crisis in the United States	Unknown	On average psychological distress increased significantly by 0.27 standard deviations (95% CI [0.23,0.31], p < .001) from March 10–18 to April 1–14, 2020 as the COVID-19 crisis emerged and lockdown restrictions began in the US.
Shevlin et al., 2021	UK adults	Three waves; T1 (March 21 −28 2020, during first week of first UK lockdown), T2 (April 22 – May 1 2020,,) and T3 (July 9 – 23 2020)	Longitudinal, N = 2025 at T1, N = 1406 at T2 and N = 1166 at T3	Clinically relevant levels of anxiety-depression (PHQ-ADS) and COVID-19 related PTSD (ITQ) over the first 4 months of the pandemic	Unknown	20.7% of the participants met the criteria for anxiety-depression at W1 with no significant change at W2 (18.6%) or W3 (20.0%). 16.8% of the participants met criteria for COVID-19 related PTSD at W1 and this percentage decreased to 15.8% at W2 and 14.4% at W3. The ITQ mean scores were similar at W1 (M = 4.58) and W2 (M = 4.51), but decreased at W3 (M = 4.07), with the mean at W3 being significantly lower than the mean at W1.
Luchetti et al., 2020	US adults	Three waves; T1 (January 31 – February 10 2020,, before the COVID-19 outbreak), T2 (March 18 – 29 2020, during the “15 Days to Slow the Spread” campaign) and T3 (April 23 – 29 2020, (during the “stay-at-home” policies of most states)	Longitudinal observational cohort, N = 1545 (mean age: 53.68 years (± 15.63, 45% female)	Change in loneliness in response to the social restriction measures taken to control the coronavirus spread	Unknown	Despite some detrimental impact on vulnerable individuals, in the present sample, there was no large increase in loneliness across the three assessments (d = 0.04, p > 0.05) but remarkable resilience in response to COVID-19.