Psychological impact of the COVID-19 pandemic on individuals with serious mental disorders: A systematic review of the literature

Table 1 Results of the database search concerning the mental health outcomes of individuals with serious mental illness

Ref.	Country or area, time	Psychiatric disorders	Methods; relevant questionnaires and COVID-19-related variables	Results	Limitations
Asmundson et al[67]	Canada and United States, March 21–April 1, 2020 (during the lockdown)	Affective disorders (BD and MDD) and anxiety-related disorders	Cross-sectional case-control online survey of 700 individuals with anxiety-related disorders, 368 individuals with affective disorders and 500 HC; PHQ-4, CSS, self-constructed questionnaires to measure self-isolation distress and coping strategies	Individuals with anxiety-related disorders experienced more COVID-19-related stress, fear, and PTSD symptoms than individuals with affective disorders and HC. Individuals with affective disorders had more PTSD symptoms and fear of socioeconomic consequences than HC. Patients with both BD and MDD exhibited more voluntary self-isolation and stress related to it. Individuals with psychiatric disorders and HC did not differ in the perceived effectiveness of their coping behaviour.	Self-report and not clinical evaluation of mental health, data about comorbidities was not gathered
Burrai et al[76]	Italy, April–May, 2020 (during the lockdown)	SZ and other psychotic disorders	Cross-sectional online survey of 77 patients with psychotic disorders and 100 HC; DASS-21, BRCS, COVID-19: Risk Perception (2 items based on Cho and Lee, 2015, and Liao, 2014), self-constructed questionnaire measuring worry	Patients with psychotic disorders were less stressed, more anxious, more worried about the current situation, and perceived the risk of being infected with COVID-19 as higher than HC. Participants with psychotic disorders living in communal residencies were supported by both their cohabitants and mental health professionals, remained adherent to their medication treatment, and possessed knowledge about the consequences of COVID-19.	Significant group differences in gender and education level, geographical limitations, observational design does not allow the determination of causality
Carmassi et al[42]	Italy, April 1-30, 2020(during the lockdown)	BD	Telepsychiatry-based cross-sectional clinical interviews and self-reports per e-mail of 100 patients with BD regarding post-traumatic stress symptoms (PTSS); IES-r, GAD-7, HAMD, YMRS	Acute PTSS were experienced by 17% of participants, which was related to COVID-19-related work/financial difficulties as well as anxiety, reported by 26% of participants. Acute symptoms of mania seemed to be protective. Furthermore, 17% of participants reported depressive symptoms.	Small sample size, self-report instruments were less accurate than an assessment by a clinician, not all COVID-19-related stress factors were considered, there was no control group
Chang et al[54]	Taiwan, March 23– April 23, 2020 (during the lockdown)	SMI and other disorders	Cross-sectional survey of 400 individuals with mental illness (242 with SZ, 67 with BD, 28 with MDD, and 63 with others); DASS-21, FCV-19S, BCIS, PCIBS	Participants who believed more strongly in the obtained COVID-19 information from newspapers, television, and online sources were more fearful of the disease. A higher level of fear was associated with more symptoms of depression, anxiety, stress, and less frequent behaviour concerning prevention.	Newly constructed questionnaires by using simple measures (BCIS, PCIBS), lack of examination of test-retest reliability (BCIS, SCIBS, FCV-19S) self-reported data, cross-sectional design does not allow the determination of causality
Chang et al[55]	Taiwan, March 23– June 30, 2020 (during the lockdown)	SMI, anxiety disorder, and substance use disorder	Cross-sectional survey of 414 patients with psychiatric disorders (197 with SZ, 141 with substance use disorder, 35 with BD, 34 with MDD, and 7 with anxiety disorder); DASS-21, SSS-S, FCV-19S, BCIS, PCIBS	Preventive behaviours recommended by the World Health Organisation could be explained by both COVID-19-related fear and trust in sources of information concerning this disease in individuals with SMI. COVID-19-related fear could be explained by trust in sources of information and self-stigma.	Cross-sectional design does not allow the determination of causality, self-report, bias (common variance, recall, social desirability), stable conditions do not allow generalizability, geographic limitations
Chen et al[74]	Taiwan, January–May, 2020 (during the lockdown)	MDD	Long-term follow-up study (structured interviews, at least three follow-ups over a period of three years) of a cohort of 116 patients with treatment-resistant MDD; structured interview about COVID-19-related changes and impact on participants’ lives (physical, psychological, and social)	Patients with depression had confidence in the COVID-19-related prevention strategies of the government. They felt distressed about pandemic-related news reports. Patients with MDD have been found to be at a higher risk for suicidality, although the pandemic had a positive impact on some patients as well.	Time limit on interviews and therefore not sufficient collection of variables
Costa et al[64]	United States, last week of March 2020 (during the lockdown)	SMI, anxiety disorder, PTSD, OCD, borderline personality disorder, and other disorders	Cross-sectional online survey of 193 individuals with psychiatric disorder (162 with anxiety disorder, 103 with MDD, 78 with BD, 77 with PTSD, 25 with OCD, 24 with BPD, 3 with SZ, and 29 with other disorders; COVID-19-related variables: Self-constructed questionnaires to measure fear, concerns, and social situation	Most of the participants had concerns about their illness and the pandemic. Notably, they were concerned about COVID-19-related service disruption. especially individuals with MDD, who feared a shortage of medication. The diagnosis of MDD was associated with the fear of getting sick. Not coping well was related to feeling socially isolated and worry about not receiving mental health care as well as experience worse psychiatric symptoms. Staying in touch with others by using social media and text messages were seemingly the best communication methods for individuals with coping difficulties related to COVID-19.	Self-constructed questionnaires, self-reported mental illness
Di Nicola et al[73]	Italy, April 27-29, 2020 (directly after seven weeks of strict lockdown)	Affective disorders (BD and MDD)	Cross-sectional online survey of 59 remitted patients with MDD and 53 euthymic individuals with BD; K10, medical records, COVID-19-related variables: Lockdown conditions (living alone, changes in work routines, and working on the frontline)	In the sample, 25.9% of subjects experienced no likelihood of distress, 31.2% experienced mild and 42.9% moderate-to-severe likelihood of distress. Severe distress was predicted by low vitamin D levels and MDD diagnosis. Higher levels of distress were more frequently found in individuals who had a longer duration of psychiatric illness, were living by themselves during the lockdown, and had the habit of smoking.	Lack of longitudinal follow-up, self-constructed questionnaires, not all confounding variables for the relation between vitamin D levels and distress were included
Franchini et al[69]	Italy, March 9– April 9, 2020 (during the lockdown)	Affective disorders (BD and MDD)	Telephone-based, non-standardized survey of 101 euthymic patients with affective disorders; self-constructed questionnaires measuring emotional stressors and unpleasant lockdown experiences	The most frequently reported stress factor was frustration, which was significantly associated with unemployment, affecting two third of participants. Somatization, heightened alertness, psychic anxiety, and bad mood were related to unemployment as well. Associations between young age and anxiety, increased alertness, and monetary concerns could be found. The participants were satisfied with both the received supplies and information about the pandemic.	Non-standardized survey and therefore problems with generalization
Frank et al[61]	Germany, 2nd, and 3rd week of March 2020 (during the lockdown)	SMI, addictive disorders, and others	Cross-sectional, standardized interviews with 196 individuals with mental illness (121 with AD, 41 with SZ, 21 with addictive disorder, and 13 with others); CGI	More than half of participants were feeling more distressed than before the pandemic. Among individuals with affective disorders, 25% had sleeping problems.	Not mentioned
González-Blanco et al[62]	Spain, March 19-26, 2020 (during the lockdown, 5 d after the beginning)	SMI: Severe mental disorder (SMD: SZ and BD), and common mental disorder (CMD: MDD and anxiety)	Cross-sectional online survey of 125 individuals with SMD (65 with BD and 60 with psychotic disorders), 250 with CMD (125 with depression and 125 with anxiety), and 250 HC; DASS-21, IES, lifestyle variables	Individuals with SMD reported higher levels of anxiety, depression, and stress than HC, but lower levels than individuals with CMD. After confounding variables were controlled, HC had less anxiety than individuals with SMD with no other differences in psychological factors. In individuals with SMD, anxiety was related to being single, suffering from COVID-19 symptoms, and increased stress levels. Many individuals with SMD (87.2%) could relish free time, however the percentage of HC who could, was higher (94%).	Selection bias and limited representativeness through selective access to digital resources, self-reported diagnoses and psychiatric symptoms, binary scales instead of Likert-type scales to assess behaviour
Hamm et al[77]	United States, April 1-23, 2020 (during the lockdown)	MDD	Semi-structured qualitative interviews with 73 older adults (age > 60) with MDD, comparison with pre-pandemic data; PHQ-9, PROMIS anxiety scale	Patients with MDD had a lower quality of life during the pandemic than before, but did not differ in depression, anxiety, and suicidal ideation symptoms. They were resilient and mostly socially connected, worried about both contracting the virus and their mental health, and were not satisfied with governmental measures.	Patients participating may have been too distressed to do so: thus, the survey did not include MDD patients with severe symptoms, distorting results; sample was not ethnically diverse
Hao et al[72]	China, February 19-22, 2020 (during the lockdown)	MDD and anxiety disorder	Cross-sectional online survey of 67 psychiatric patients (45 with mixed anxiety and depression, 19 with other anxiety disorders, and 12 with MDD) and 109 HC; IES-R, DASS-21, ISI	Psychiatric patients showed more symptoms of depression, anxiety, stress, PTSD, and insomnia than HC. Additionally, they had more concerns about their physical health and higher levels of anger, impulsivity, and suicidal ideation than HC. The diagnostic criteria for PTSD were possibly fulfilled by more than 30% of participants with mental illness. More than 25% of them had moderate to severe insomnia.	Generalisation not possible, no biological samples were obtained, low response rate due to online recruitment, geographical limitation, cross-sectional study
Hölzle et al[68]	Germany, middle of May 2020 (during the lockdown with loosened restrictions)	SMI, psychotropic dependence, and other disorders	Cross-sectional assessment of 139 psychiatric inpatients (89 with affective disorders, 26 with SZ, 17 with psychotropic substance abuse, and 7 others); CGI, PSS, SRS	The disorders lead to differences in the CGI-score (M = 4.9, SD = 1.0), however, women had higher scores than men. Individuals with AD had the highest levels of both perceived stress and related somatic complaints. Higher CGI-scores were not associated with stress, but with stress-related somatic problems. These correlations were especially high in individuals with AD, and non-existent in individuals with SZ.	Not mentioned
Iasevoli et al[59]	Italy, April 13-17, 2020 (during the lockdown, one month after the beginning)	SMI	Telephone-based cross-sectional case-control study of 205 patients with SMI, 51 first-degree relatives, and 205 HC; PSS, GAD-7, PHQ-9, SPEQ	Individuals with SMI were of lower economic status and had more concordant diseases than HC. They experienced more symptoms of anxiety, depression, stress, and paranoia than HC. COVID-19-related stress was an important predictor for anxiety. Comorbidities had an independent influence on anxiety, depression, and stress. Caregivers showed more depressive symptoms than HC.	Not mentioned
Korsnes et al[50]	Norway, March–June, 2020 (during and after the lockdown)	SMI, anxiety, and other disorders	Cross-sectional online survey of 19 older (age > 65) psychiatric outpatients (15 with MDD, 2 with cognitive deficit/dementia, 1 with anxiety, and 3 with other diagnoses), 14 inpatients (12 with MDD, 6 with anxiety, 2 with BD, 2 with psychosis, and 1 with another diagnosis), and 46 employees working with them; COVID-19-related variables: Self-constructed questions about fear, prevention measures, risk, and consequences	The majority of patients approved of the strict prevention measures, were not afraid of being infected with COVID-19, and did not think that they would die in case of an infection. Psychiatric patients were generally less concerned about the repercussions of COVID-19 on their health than healthcare employees. Few were very worried, did not welcome the governmental measures, thought the infection risk to be increased the clinic, and/or saw a negative impact on their daily life.	Small sample size, generalisation not possible, self-constructed questionnaires, different times of response (similar measures, but different medial climate)
Liu X. et al[82]	China, January 30-February 21, 2020 (during the lockdown)	SZ	Retrospective double centre study of hospitalized SZ patients: 21 suspected to have COVID-19 (11 confirmed), and 30 without suspected COVID-19 infection; PANSS, PSS, HAMA, HAMD, PSQI, COVID-19-related variables: Treatment, symptoms	Schizophrenic patients with suspected COVID-19 had higher levels of stress, depression, and anxiety, and a worse quality of sleep, even after the adjustment for the use of benzodiazepines	Retrospective study: Longitudinal studies and follow-up are needed, assessments for the groups were performed by different doctors
Liu et al[70]	United States, April 13–May 19, 2020 (during and after the lockdown)	MDD, anxiety disorder, post-traumatic stress disorder, attention deficit hyperactivity disorder, insomnia, and others	Cross-sectional online survey of 898 young adults: 44.6% with mental illness: 38.2% with treatment and 6.2% without treatment (31.7% with depression, 29.0% with anxiety, 8.0% with PTSD, 6.9% with ADHD, 6.7% with insomnia, and 17.7% with others), 23.4% with a suspected mental illness, and 32.2% HC; PHQ-8, GAD-7, PCL-C, MOS-SS, HRQoL, COVID-19-related variables: Self-constructed questionnaires to measure worry and grief	Individuals with a diagnosed (treated or untreated) or suspected psychiatric illness were more likely to have symptoms of depression, anxiety, and PTSD than HC. Individuals who were diagnosed with or suspected to have a psychiatric illness experienced more worries connected to COVID-19, more sleeping problems, and a lower health-related quality of life.	No generalizability due to sample from possible COVID-19 “hotspots”, variability in circumstances concerning the time of receiving treatment and/or diagnosis, no diagnosis in suspected cases, no information about treatment and adherence to it, no baseline data for comparison
Ma et al[81]	China, January 10–April 30, 2020(before, during, and after the lockdown)	SZ	Case-control assessment of 30 SZ inpatients who were isolated for 14 d and 30 who were not, with a longitudinal comparison of isolated patients before and after isolation; CPSS, PANSS, HAMD, HAMA, PSQI	The isolation group experienced more stress, anxiety, and depression than the non-isolation group. After isolation, patients with SZ exhibited higher levels of stress and C-reactive protein and had a lower quality of sleep.	Small sample size, short observation period, several inflammatory markers were not sufficiently researched with regard to their impact on social isolation and their correlation with the mental health
Matei et al[53]	Romania, March 16–May 14, 2020 (during the lockdown)	SMI and severe AUD	Cross-sectional survey of 115 male psychiatric inpatients (65 with SMI and 50 with severe AUD) and 57 HC; self-constructed questionnaires to measure general knowledge about COVID-19, prevention, and the ability to identify false statements about COVID-19	Patients with SMI were less informed about general knowledge as well as prevention of COVID-19 than HC. Additionally, they were less able to single out false information about COVID-19. Apart from patients with severe AUD being as informed about prevention measures as HC and therefore more informed than patients with SMI, there was no difference between these two groups.	Small sample size, all-male sample, potential selection bias due to the method of selecting HC from residential areas and shopping centres, not representative of all psychiatric illnesses
Muruganandam et al[52]	India, at the end of April 2020 (during the lockdown, one month after the beginning)	SMI	Telephone-based cross-sectional survey of 132 patients with SMI and their caregivers; self-constructed interview about COVID-19: Knowledge, perceived social support and aggression, psychiatric symptoms, somatic status	Among the participants, 8.3% did not know about the current pandemic and 75% were neither worried about being infected nor knowledgeable about the symptoms. Additionally, 66% possessed little knowledge about prevention and 20% did not know about the way of transmission. A lack of knowledge was associated with low socioeconomic status, little education, and meager social support. A third exhibited symptoms indicative of a recurrence of their illness.	Small sample size, lack of longitudinal follow-up, lack of healthy control group, self-constructed interview, assessment was not structured, dependence on caregivers’ reports on patients’ situations
Mutlu and Anıl Yağcıoğlu[36]	Turkey, March 23–April 13, 2020 (before and during the lockdown)	SMI	Telephone-based cross-sectional interviews of 155 individuals with SMI (131 with SZ and 24 with BD) and retrospective data analysis; collection of data about clinical characteristics, medication adherence, and relapse	The total relapse rate in the first trimester of the pandemic was 11% (n = 15 with SZ, n = 2 with BD), with the most frequently related influence being the interruption of antipsychotic medication (59%). However, the relapse rate did not differ from the rate in 2019. Individuals suffering from a relapse had been hospitalized at a more recent date than the individuals who remained stable. Very few patients (n = 2) attempted suicide or had suicidal thoughts during the pandemic.	Not mentioned
Orhan et al[77]	Netherlands, January 1, 2018– December 31, 2018 and April 2020 (during the lockdown)	BD	Baseline interviews and cross-sectional survey of 81 older (age ≥ 50) patients with BD; YMRS, CES-D, BAI, SPS, LS, PMS, UC, NEO-FFI, COVID-19-related variables: Fear, mental health impact, positive coping (see Pan et al, 2020)	Older patients with BD experienced less psychiatric symptoms during the pandemic compared to the baseline. Loneliness, not having children, passive coping style, low mastery, and neuroticism were associated with more psychiatric symptoms.	Large interval between the collection of baseline data and the interviews during COVID-19 pandemic, only short-time impact, relatively small sample
Pan et al[25]	Netherlands, 2006–2016 and April 1–May 13, 2020 (during and after the lockdown)	MDD, anxiety disorder, OCD	Three longitudinal studies with several follow-ups and a cross-sectional online survey of 1181 individuals with psychiatric disorders (1051 with MDD or anxiety and 130 with OCD) and 336 HC during the pandemic; QIDS, BAI, PSWQ, DJGLS	Participants with psychiatric disorders had higher symptoms of depression, anxiety, worry, and loneliness than HC. This was the case before as well as during the pandemic, however, the severity of symptomatology did not increase over time, even showing a slight decrease during the lockdown. In comparison, HC experienced a greater decrease of their mental health than individuals with mental illness.	Different modes of collecting data during face-to-face interviews compared to online surveys during the pandemic, low response rate, no standardised assessment for mental disorders, symptom severity was measured by number of diseases
Pellegrina et al71]	France, during the first wave of the pandemic (during the lockdown)	MDD and anxiety disorder	Retrospective survey of 85 individuals with MDD or anxiety disorder; STAY-YA, Beck BDI-II, COVID-19-related variables: Perception, psychological resources, life conditions	Some participants experienced a worsening of their mood during the lockdown. More pronounced symptoms of both anxiety and depression, sleep disorders and addiction could be found.	Retrospective study: Longitudinal studies and follow-up are needed,
Pinkham et al[57]	United States, December 4, 2018–now (still ongoing) and April 3–June 4, 2020 (during and after the lockdown)	SMI	Baseline interviews, online surveys administered three times a day during a 10- or 30-d period before pandemic EMA, and ID-5 (psychosis module), PANa telephone-based cross-sectional survey during the pandemic of 148 patients with SMI (92 with SZ or schizoaffective disorder and 56 with affective disorder); baseline: MINI, SCSS, YMRS, MADRS, SUMD; EMA: Questionnaires about social life, mood, psychiatric symptoms, substance use well-being, and sleep; phone survey was a combination of baseline and EMA	Both affective and psychotic symptoms as well as the duration of sleep remained stable over time. An increase in the number of substances used and psychological well-being was reported, the latter of which was related to female gender and more time spent with other people. The two disorders did not differ in patterns concerning stability or change.	Data was collected early; longer longitudinal studies should be conducted
Pogany et al[63]	Hungary, August 1–September 15, 2020 (after the lockdown)	SMI, anxiety disorder, personality disorder, and others	Retrospective survey of 438 psychiatric patients (39.4% with SZ, 34.6% with affective disorder, 25.0% with anxiety disorder, 0.9% with personality disorder, and 2.7% with others); COVID-19-related variables: “Problem Evaluation Scale” to measure fear, isolation, and healthcare	A third of psychiatric patients felt a worsening of their condition during the time of governmental physical distancing measures, with 12% of them not believing it was related to these measures. Half of patients were feeling distressed because of loneliness and isolation, notably more woman than men. The percentage of individuals with psychiatric disorders who were concerned about their financial situation was higher that the percentage of those who were concerned about own health. Younger patients (age < 50 yr) experienced on average worsened health, were feeling more fearful, and had more difficulties adapting than older patients. In comparison to patients with psychotic disorders, patients with affective disorders were feeling more vulnerable. Patients with SZ had the least problems with a lack of information about COVID-19.	Not mentioned
Quittkat et al[58]	Germany, April 2-May 6, 2020(during the lockdown)	MDD, SZ, SP, OCD, GAD, SAD, IA, ED, panic disorder and PA, and BDD	Cross-sectional online survey and retrospective data assessment of 1207 individuals with psychiatric disorders (586 with depression, 135 with GAD, 86 with SAD, 83 with PA, 62 with ED, 47 with OCD, 30 with IA, 16 with BDD, 6 with SP, and 135 others) and 1026 HC; BDSI, CAHSA, DASS-21 (depression subscale), EDE-Q – 2nd ed., PHQ (Panic Model and Stress Subscale), PSWQ-d, SIAS, SPhS, WI, Y-BOCS	All participants had on average fewer social contacts and did not go grocery shopping as often as before the pandemic. All individuals reported augmented levels of psychosocial stress, worried more about COVID-19, and were more fearful of contracting this illness than HC. Among individuals with depression, a quarter perceived an improvement, whereas 57.51% experienced a decrease of their mental health and 45.9% felt the need for more therapeutic support. Individuals with SZ reported mostly no or only slight changes in their mental health and did not find further therapeutic support to be necessary.	Small sample sizes of some groups, retrospective data assessment, self-identification of mental disorders, individuals with mental illness and HC were not matched, possible gender bias, selection bias through method of recruitment, online assessment
Riblet et al[78]	United States, October 2019–March 2020 and April 23–May 4 (before and during the lockdown)	SMI	Longitudinal interviews of 11 veterans with SMI (5 with MDD, 5 with BD, and 1 with psychotic disorder), with three in-person interviews conducted before the stay-at-home order (baseline, 1- and 3-mo follow-up) and one telephone-based interview during the lockdown; baseline: MINI; later additions: Hopelessness, social connections, treatment engagement, and suicidal ideation	There were no relevant changes concerning psychiatric symptoms during the pandemic compared to before. Few participants, who were significantly older (M = 71.7 yr) experienced an increase in symptomatology.	Small sample size, geographical limitation: low infection rate in Northern New England, participants consisted solely of veterans with possibly easier treatment access, participants had been hospitalized because of their illness, no long-term follow-up
Rohde et al[60]	Denmark, February 1–March 23, 2020 (before and during the lockdown)	SMI, stress-related and adjustment disorders, personality disorders, autism, ED, hyperkinetic disorder, and others	Analysis of clinical notes of 14561 psychiatric inpatients, with 918 of them being further analyzed (198 with SZ, 130 with MDD, 68 with BD, and 522 others); screening of clinical notes for COVID-19-related psychiatric symptoms	The final number of patients with notes describing pandemic-related psychopathology was 918, with two thirds of them being female. Most notes contained symptoms related to logistical problems. The most common symptoms were anxiety (n = 539), stress (n = 174), delusions (n = 149), depression (n = 146), suicidality (n = 102), and obsessive-compulsive symptoms (n = 85).	Lack of systematic assessment for COVID-19-related psychopathology
Solé et al[56]	Spain, May 14–June 8, 2020 (during the lockdown)	SMI (SZ or BD and MDD and/or anxiety)	Cross-sectional online survey of 206 individuals with psychiatric illness (148 with BD or SZ and 50 with MDD or anxiety) and 413 HC; self-constructed questionnaires for psychological distress (inspired by GAD-7 and PHQ-9), trauma experiences (inspired by EGS-R), psychotic-like experiences (adapted from CAPE-42), resilience (derived from BRS and RS-14), affective temperament (inspired by TEMPS-A), perceived family environment (inspired by FES), cognitive reserve (based on CRASH), physical aggressiveness (derived AQ); lifestyle	In comparison to HC, individuals with psychiatric disorders reported less use of coping strategies, such as having a routine, social interactions, and a healthy lifestyle. Furthermore, they experienced more symptoms of depression and anxiety during the lockdown. They showed more frequently changes of sleep patterns, weight gain, and tobacco consumption than HC. Individuals with depression and/or anxiety were more distressed and concerned about the future, suffered from more sleeping problems, and exercised more than individuals with SZ or BD.	Lack of generalizability, self-reported mental illness, different restrictions at different times when conducting the survey, lack of longitudinal follow-up, possible gender bias, questionnaires were only based on validated scales and not these scales themselves were used
Somer et al[80]	Mostly in the United States, Italy, Turkey, UK, and Canada, mid-April–mid-May 2020 (during the lockdown)	MDD, anxiety disorder, MD	Cross-sectional online survey of 326 individuals with MD and 546 HC (417 with anxiety disorders, 226 with MDD, and 189 with others in both groups); MDS-16, COVID-19-related variables: Questions about changes in daydreaming and psychosocial functioning	Individuals with depression and anxiety, who were suspected to have MD, were feeling an elevated urge to daydream during the pandemic and had more problems controlling it than individuals with MD and none of these disorders.	No generalizability due to sampling limitations, cross-sectional design does not allow the determination of causality, low effect size, no clinical diagnosis of MD
Van Rheenen et al[75]	Australia, April 1-4, 2020 (during the lockdown)	Affective disorders (BD and MDD)	Cross-sectional online survey of 1292 participants with a self-reported affective disorder and 3167 HC; DASS-21, PANAS, COVID-related variables: Questionnaires about primary concerns, changes in personal situation, perceptions, or behaviour	Individuals with affective disorders reported higher psychological distress than HC. Individuals with BD experienced more stress and depressive symptoms compared to individuals with depression; men with BD had more symptoms of distress and depression than women. Both groups did not differ in their mild symptoms of anxiety. Individuals with BD showed more pronounced financial concerns than individuals with depressive disorder and HC.	Self-selection and potentially selection bias, cross-sectional design led to a retrospective self-analysis of changes by the participants with no validation by the authors, self-reported affective disorders, mood disorder group was not balanced regarding gender distribution, no baseline measures of mood and lifestyle
Winkler et al[8]	Czech Republic, November 2017 and May 6– 20, 2020 (during and shortly after the lockdown)	Affective disorders (BD and MDD), anxiety disorders, and AUD	Two cross-sectional interviews of 3306 participants in 2017 (10.84% with AUD, 7.79% with anxiety disorders, and 6.57% with affective disorder) and 3,021 in 2020 (18.58% with affective disorder, 12.84% with anxiety disorders, and 9.88% with AUD); MINI, COVID-19-related variables: Lifestyle, worries, seeking of mental professional help, psychiatric symptoms	In 2020, 29.63% of individuals in Czech Republic suffered from mental illness in comparison to 20.02% in 2017. The prevalence of MDD tripled and there was no difference in the prevalence of alcohol use disorder, however, more individuals exhibited binge drinking behavior (4.07% vs 6.39%). The suicide risk rose from 3.88% to 11.88% in 2020. Having a mental disorder was associated with more worryies about COVID-19-related impacts on health and economy.	No cohort study and therefore no assessment of the development of mental illness in previously health individuals, lack of face-to-face interviews, relaxation of MINI criterion, data collection after loosening of strictest COVID-19-related measures
Zhu et al[51]	China, 28 February-6 March, 2020 (during the lockdown)	SMI	Cross-sectional online survey of 925 inpatients with SMI (657 with SZ and 268 with affective disorder) in economically less developed geographic regions; clinical characteristics, COVID-19-related variables: Self-constructed questions about prevention, knowledge, information sources	The majority of participants (84.4%) had a positive stance regarding measures for preventing COVID-19, which was related to marriage and a higher level of education. The latter was additionally associated with more knowledge about the pandemic. The main sources of information were public media and individuals’ attending physicians.	Lack of an outpatient control group, lack of examination of variables associated with attitude and knowledge pertaining COVID-19
Zou et al[66]	China, May 22-July 15, 2020 (during and after the lockdown)	SMI, organic mental disorders, and others	Cross-sectional online survey of 1063 older (age ≥ 50 yr) psychiatric patients (485 with MDD, and 578 with BD, SZ, organic mental disorders, and others); Patient Health Questionnaire (PHQ-9), ISI, NPRS, WHOQOL-BREF, self-constructed questionnaires to measure fatigue, COVID-19-related variables: Access to psychiatric services, treatment adherence, concerns	Nearly half of participants were feeling fatigue (47.1%), which was associated with a lower quality of life. A higher level of fatigue was related to more severe symptoms of depression, insomnia, and pain.	Results cannot be generalized, as the patients were of older age, cross-sectional design does not allow the determination of causality, several factors of importance were not researched due to logistical reasons

BD: Bipolar disorder; HC: Healthy controls; MDD: Major depressive disorder; OCD: Obsessive-compulsive disorder; PTSD: Post-traumatic stress disorder; SMI: Serious mental illness; questionnaires: AQ: Aggression Questionnaire; ASRM: Altman Self-Rating Mania Scale; BAI: Beck Anxiety Inventory; BCIS: Believing COVID-19 Information Scale; BDI-II: Beck Depression Inventory II; BDSI: Body Dysmorphic Symptoms Inventory; BRCS: Brief Resilient Coping Scale; BRS: Brief Resilience Scale; CAHSA: Continuum of Auditory Hallucinations-State Assessment; CAPE-42: Community Assessment Psychic Experiences; CES-D: Center for Epidemiologic Studies Depression Scale; CGI: Clinical Global Impression; CPSS: Chinese Perceived Stress Scale; CRASH: Cognitive Reserve Assessment Scale in Health; CSS: COVID Stress Scales; DASS-21: Depression; Anxiety; and Stress Scale-21 Items; DJGLS: De Jong Gierveld Loneliness Scale; EDE-Q: Eating Disorder Examination-Questionnaire – 2^nd Ed.; EGS-R: Posttraumatic Stress Disorder Symptom Severity Scale-Revised; FCV-19S: Fear of COVID-19 Scale; FES: Family Environment Scale; GAD-7: Generalized Anxiety Disorder-7; HAMA: Hamilton Anxiety Rating Scale; HAMD: Hamilton Depression Rating Scale; IES(-r): Impact of Event Scale(-revised); HRQoL: Health-related quality of life; ISI: Insomnia Severity Index; K10: Kessler 10 Psychological Distress Scale; LS: Loneliness Scale; MADRS: Montgomery-Asberg Depression Rating Scale; MDS-16: Maladaptive Daydreaming Scale; MINI: Mini International Diagnostic Interview; MOS-SS: Medical Outcomes Study Sleep; NEO-FFI: NEO-Five Factor Inventory; NPRS: Numeric Pain Rating Scale; PANSS: Positive and Negative Syndrome Scale; PCIBS: Preventive COVID-19 Infection Behaviours Scale; PCL-C: PTSD Checklist – Civilian Version; PHQ-4/8/9: Patient Health Questionnaire-4/8/9; PMS: Pearlin Mastery Scale; PSQI: Pittsburgh Sleep Quality Index; PSS: Perceived Stress Scale; PSWQ: Penn State Worry Questionnaire; QIDS: Quick Inventory of Depressive Symptoms; RS-14: Resilience Scale; SCID-5: Structured Clinical Interview for DSM-5; SIAS: Social Interaction Anxiety Scale; SPEQ: Specific Psychotic Experience Questionnaire; SPS: Social participation scale; SPhS: Social Phobia Scale; SRS: Stress-Related Somatic complaints; SSS-S: Self-Stigma Scale-Short; STAY-YA: Spielberger’s anxiety questionnaire (French: L’échelle d’anxiété état de Spielberger); SUMD: Scale to Assess Unawareness of Mental Disorder; TEMPS-A: Temperament evaluation of Memphis, Pisa, Paris, and San Diego-autoquestionnaire; UC: Utrechtse Copinglijst; WHOQOL-BREF: World Health Organization Quality of Life-brief version; WI: Whitely Index; Y-BOCS: Yale-Brown Obsessive Compulsive Scale – Symptom Checklist; YMRS: Young Mania Rating Scale.