Table 1.

Characteristics of Included Trials.

Author Dates Country(ies) Registration	Participants	Intervention Comparator	COVID-19-specific and Scalability Aspects: Delivery Format Individual/Group/Self-admin Professional/Lay/No personnel	N Analyzed: Intervention/Comparator	Outcome Time to Follow-up Post-Randomization and Domain(s)a	Mean (SD) Age	% Female or Women
Kahlon et al. 30 07/2020 to 09/2020 USA NCT04595708 (retrospective)	Homebound older adults receiving services through a Meals on Wheels organization	Volunteers trained in empathetic conversational techniques called participants over 4 weeks, daily for the first 5 days then 2–5 calls per week. Calls were targeted to be less than 10 min; however, callers reported that calls could run longer No calls	Designed to address loneliness in homebound meal recipients isolated due to COVID-19 Telephone Individual Lay volunteer delivery	120/120	4 weeks Anxiety; Depression; Mental Health Function; Loneliness	69 (12)	79%
Thombs et al. 31 04/2020 to 07/2020 Canada, USA, France, UK, Australia, 7 others NCT04335279	Adults with systemic sclerosis and at least mild anxiety (PROMIS Anxiety 4a v1.0  ≥  55) recruited from a multinational cohort	4-week, 3× per week, 90-min videoconference group sessions focusing on leisure activities, mental health coping, and social support Waitlist	Designed with patients to target COVID-19 anxiety through evidence-based strategies and social support Videoconference Group Mixed professional and peer volunteer delivery	86/86	4 weeks and 10 weeks Anxiety; Depression; Loneliness; Fear	55 (11)	94%
Wahlund et al. 32 05/2020 to 07/2020 Sweden NCT04341922	Swedish adults with difficulty controlling worry about COVID-19, excluding those with moderate to severe depression or suicide risk, recruited via media from general population	3 weeks of self-directed, established online cognitive behavioural intervention for worry-related problems plus additional modules adapted specifically for dysfunctional COVID-19 worry Waitlist	Evidence-based cognitive behavioural strategies to address worry adapted for dysfunctional COVID-19 worry Internet Self-administered No personnel to deliver	335/335	3 weeks COVID-19 Anxiety; Depression	46 (14)	82%
Al-Alawi et al. 33 04/2020 to 07/2020 Oman NCT04378257	Adults aged 18–65 from Oman with PHQ-9 ≥ 12 or GAD-7 ≥ 10 and no pre-existing mental health or substance use disorders or suicide ideation, recruited from a list of online survey respondents	6 weekly videoconference-based individual therapy sessions based on principles of cognitive behavioural therapy and acceptance and commitment therapy Minimal: weekly newsletter with self-help tips	No COVID-19 adaptations reported Videoconference Individual Professional	22/24	6 weeks Anxiety; Depression	29 (9)	78%
Pheh et al. 34 NR Malaysia Not registered	Adults recruited from social media	Single ultra-brief online mindfulness-based journaling exercise Single ultra-brief online journaling exercise not based on mindfulness	Standard mindfulness journaling minimally adapted to reflect on movement restrictions Internet Self-administered No personnel to deliver	33/28b	3 weeks Anxiety; Mental Health Function; Fear	NR	NR
Pizarro-Ruiz et al. 35 04/2020 to 05/2020 Spain Not registered	Students in social education or nursing from a single university, recruited via email	Daily app-based 15-min mindfulness sessions for 2 weeks using publicly available app Daily app-based 15-min mind training (e.g., attention, memory) sessions for 2 weeks using publicly available app	No COVID-19 adaptations reported Internet Self-administered No personnel to deliver	89/75	2 weeks Mental Health Function	22 (6)	83%
Shabahang 36 NR Iran Not registered	Students from a single university with significant coronavirus anxiety who were not receiving active psychological treatments; recruitment method not provided	Group-based 90-min cognitive behavioural therapy sessions focused on health anxiety delivered 5 days per week for 2 weeks Waitlist	Included lecture by virologist on COVID-19 but no other COVID-19 adaptations reported Not reported Group Professional	75/75	2 weeks Anxiety; Depression	NR	NR
Vukčević Marković et al. 37 NR Serbia ISRCTN17898730 (retrospective)	Serbian adults recruited via social media	5 online 20-min expressive writing sessions over 2 weeks (3 days between sessions), during which participants were instructed to write anything that came to mind regarding COVID-19 No intervention	Minimal adaptation of expressive writing by using COVID-19 theme Internet Self-administered No personnel to deliver	2 weeks 48/56 4 weeks 36/38	2 weeks and 6 weeks Anxiety; Depression; Mental Health Function; Stress	32 (10)	74%
Yang et al. 38 NR China Not registered	Chinese students from a single university at home due to COVID lockdown; recruitment method not provided	Audio-recorded 30-min mindfulness-based stress reduction session once every 2 days for 10 days No intervention	Minimal adaptation by including mindfulness exercise on accepting COVID-19-related negative thoughts and affect Internet Self-administered No personnel to deliver	53/51	2 weeks Anxiety; Depression; Mental Health Function; Stress	19 (1)	53%

GAD-7  =  Generalized Anxiety Disorder scale; NR  =  not reported; PHQ-9  =  Patient Health Questionnaire-9.

^a Specific scales used in each trial are shown in Table 3.

^b Only follow-up data (N  =  61), but not results from assessment immediately following the single-session intervention, were eligible for inclusion and are reported here.