Table 1 Characteristics of the studies included

Germany

Ravens-Sieberer,

2022 [21]

Cohort study, German COPSY study

PP: 994 (47.8)

DP1: 1,018 (49.6)

DP2: 1,073 (49.2)

DP3: 1,173 (48.4)

PP: NI

DP1: Mean (years) ± SD, 12.3 ± 3.3

DP2: Mean (years) ± SD, 12.7 ± 3.3

DP3: Mean (years) ± SD, 14.8 ± 2.3

Age range (years):

11 to 19

DP1:

5–6/2020

DP2: 12/2020—1/2021

DP3:

9–10/2021

DP1

Stringency Index:

59.7 (57.4 to 59.7)

School Closure Index:

2.0 (2.0 to 2.0)

DP2

Stringency Index:

83.1 (82.4 to 85.2)

School Closure Index:

3.0 (3.0 to 3.0)

DP3

Stringency Index:

49.2 (37.0 to 60.2)

School Closure Index:

1.3 (1.0 to 3.0)

2017 (nationwide, longitudinal, representative BELLA study)

both study samples (BELLA and COPSY) are representative samples of German children and adolescents

General anxiety symptoms

Screen for Child Anxiety Related Disorders (SCARED);

Psychometric properties [69];

Self-reported

Moderate

Witte,

2022 [56]

Cross-sectional study, medical record data from a health insurance company

PP: 533,701 (48.6)

PP: 332,945 (48.6; in-patient treatment)

DP1: 545,626 (48.6)

DP1: 339,361 (48.6; in-patient treatment)

DP2: 343,642 (48.5; in-patient treatment)

Age range (years):

5 to 17

DP1: 2020

DP2: 2021

DP1:

Stringency Index:

51.8 (0 to 76.9)

School Closure Index:

1.6 (0.0 to 3.0)

DP2:

Stringency Index:

67.0 (46.3 to 85.2)

School Closure Index:

1.9 (1.0 to 3.0)

2019

Cross-sectional population samples

Clinically relevant anxiety symptoms

Paediatric visit/ Hospitalisation rate

ICD-10: F40/41;

NI for psychometric properties (International Statistical Classification of Diseases and Related Health Problems [ICD]);

Paediatric reported

Moderate

Kostev,

2021 [44]

Cross-sectional study, medical record data from the Disease Analyzer database (IQVIA)

PP: 206,528 (39.2; prevalence, incidence)

DP: 203,742 (39.7; prevalence, incidence)

PP: Mean (years) ± SD, 6.6 ± 4.9

DP: Mean (years) ± SD, 6.7 ± 5.0

Age range (years): 2 to 17

4/2020 to 12/2020

Stringency Index:

62.2 (49.5 to 82.4)

School Closure Index:

1.8 (1.0 to 3.0)

4/2019 to 12/2019

Cross-sectional population samples

Clinically relevant anxiety symptoms

Paediatric visit

ICD-10: F41;

NI for psychometric properties (International Statistical Classification of Diseases and Related Health Problems [ICD]);

Paediatric reported

Moderate

Rau,

2021 [45]

Cohort study

PP: 777 (53.3)

PP: 777 (53.3)

Mean (years) ± SD, 12.9 ± 2.0

Age range (years): 9 to 17

6–7/2020

Stringency Index:

59.7 (57.4 to 63.4)

School Closure Index:

1.9 (1.0 to 3.0)

PP1:

10–11/2019

PP2:

1–2/2020

Same population

General anxiety symptoms

Clinically relevant anxiety symptoms

Clinically relevant anxiety symptoms

Revised Child Anxiety and Depression Scale (RCADS) with anxiety subscales;

Psychometric properties [70];

Self-reported

Serious

Israel

Shoshani,

2021 [46]

2-point survey

PP: 1,537 (52)

DP: 1,537 (52)

Mean (years) ± SD, 14.0 ± 2.0

Age range (years):

11 to 17

4/2020

Stringency Index:

77.3 (75.0 to 84.3)

School Closure Index:

2.1 (2.0 to 3.0)

9/2019

Same population

General anxiety symptoms

Brief Symptom Inventory 18 (BSI-18) with the subscale anxiety;

NI for psychometric properties;

Self-reported

Moderate

Italy

Frigerio,

2022 [47]

Longitudinal study, Effect of Depression on Infants (EDI)

PP1: 94 (46.8)

PP2: 88 (46.6)

DP: 59 (45.8)

PP1:

Mean (months) ± SD, 13.7 ± 1.63

PP2:

Mean (years) ± SD, 3.5 ± 0.3

DP:

Mean (years) ± SD, 4.2 ± 0.6

4–6/2020

Stringency Index:

77.4 (67.6 to 93.5)

School Closure Index:

3.0 (3.0 to 3.0)

PP measures 1 and 2 (no detailed information)

Same population

General symptoms, subscale anxious/ depressed

Child Behavior Checklist (CBCL 1½-5), subscale anxious/ depressed;

Psychometric properties [71];

Parent-reported

Serious

Davico,

2021 [48]

Cross-sectional study

Psychiatric Emergency Department (ED) visits

PP1: 101, (61.4)

PP2:

93 (65.6)

PP3:

131 (55.0)

DP:

50 (54.0)

Median (years) (IQR)

PP1: 15.1 (13.2 to 16.6)

PP2: 14.1 (11.7 to 16.3)

PP3: 14.7 (11.9 to 16.5)

DP: 15.7 (13.2 to 16.7)

Age range (years):

0 to 18

2–4/2020

Stringency Index:

81.8 (64.4 to 93.5)

School Closure Index:

3.0 (3.0 to 3.0)

PP1: 1–2/2019

PP2: 2–4/2019

PP3: 1–2/2020

Cross-sectional population samples

General anxiety symptoms

Hospitalisation rate

ED visits due to anxiety;

NI for psychometric properties;

Paediatric reported

Critical

Crescen-tini,

2020 [49]

Online survey

PP: 721 (48.4)

DP: 721 (48.4)

Mean (years) ± SD, 10.1 ± 2.5

Age range (years):

6 to 18

4–5/2020

Stringency Index:

90.2 (75.0 to 93.5)

School Closure Index:

3.0 (3.0 to 3.0)

retrospective (final months of 2019)

Same population

General anxiety symptoms

Child Behavior Checklist (CBCL 6–18), subscale anxiety;

Psychometric properties [72];

Parent-reported

Critical

Netherlands

Luijten,

2021 [20]

Cross-sectional study

PP: 1,318 (50.1)

DP: 813 (54.6)

PP: Mean (years) ± SD, 13.1 ± 3.1

DP: Mean (years) ± SD, 13.4 ± 2.8

Age range (years): 8 to 18

4–5/2020

Stringency Index:

78.7 (78.7 to 78.7)

School Closure Index:

3.0 (3.0 to 3.0)

12/2017–7/2018 (2 studies)

PP:

2 representative studies

DP:

1 representative study (not same population)

General anxiety symptoms

Patient-Reported Outcome Measurement Information System (PROMIS), CAT V2.0-Anxiety;

Psychometric properties [73];

Self-reported

Moderate

Norway

Hafstad,

2021 [50]

Representative longitudinal survey

PP: 3,572 (50.1)

DP: 3,572 (50.1)

Mean (years) ± SD,

14.7 ± 4.1

Age range (years):

12 to 16

6/2020

Stringency Index:

42.5 (40.7 to 58.3)

School Closure Index:

1.0 (1.0 to 1.0)

2/2019

Same population

General symptoms, anxiety and depression

Hopkins Symptom Checklist (HSCL-10);

Psychometric properties [74, 75];

Self-reported

Serious

Spain

Giménez-Dasí,

2021 [51]

3-point survey

PP:206 (51.9)

DP1:66 (62.1)

DP2: 205 (53.7)

Mean months ± SD, 102.4 ± 20.2

Age range (years):

6 to 11

DP1:

3–4/2020

DP2:

12/2020–2/2021

DP1:

Stringency Index:

68.2 (11.1 to 85.2)

School Closure Index:

2.6 (0.0 to 3.0)

DP2:

Stringency Index:

72.2 (68.5 to 78.7)

School Closure Index:

1.3 (1.0 to 3.0)

12/2019 to 2/2020

Same population: PP and DP2

Subgroup of children: DP1

General anxiety symptoms

Anxiety scale ‘System of Evaluation of Children and Adolescents’ (SENA) questionnaire;

Psychometric properties [76];

Self-reported (partly with parents’ supervision)

Serious

Carrillo-Diaz,

2022 [52]

2-point-survey

213 (54.5)

Mean (years) ± SD, 14 ± 1.9

Age range (years):

11 to 17

9–12/2020

Stringency Index:

67.6 (58.8 to 78.7)

School Closure Index:

1.7 (1.0 to 3.0)

9–12/2019

Same population

General anxiety symptoms

A: State Anxiety Scale

(STAI-S);

Psychometric properties [77];

Self-reported

Critical

Switzerland

Ertanir,

2021 [53]

Longitudinal study, ‘Overcoming Inequalities with Education’ project

PP: 359 (46.2)

DP: 314 (43.0)

Mean (years) ± SD, 12.7 ± 0.7

Age range (years):

11 to 15

8–9/2020

Stringency Index:

43.1 (43.1 to 43.1)

School Closure Index:

0.0 (0.0 to 0.0)

9–10/2019

Same population

General anxiety symptoms

Hopkins Symptoms Checklist (HSCL-25), subscale anxiety;

NI for psychometric properties;

Self-reported

Moderate

Borbás,

2021 [54]

Cohort study

PP: 26 (38.5)

PP: 26 (38.5)

Mean (years) ± SD, 10.7 ± 2.5

Age range (years):

7 to 17

5/2020

Stringency Index:

69.4 (69.4 to 69.4)

School Closure Index:

0.0 (0.0 to 0.0)

3/2018 to 2/2020

Same population

General symptoms, subscale anxious/ depressed

Child Behavior Checklist (CBCL 6–18), subscale anxious/ depressed;

Psychometric properties [78];

NI

Critical

United Kingdom

Knowles,

2022 [23]

Cohort study, REACH (Resilience, Ethnicity, and AdolesCent Mental Health)

PP1: 955 (NI)

PP2: 943 (NI)

PP3: 836 (53.7)

DP: 1,069 (54.5)

Age range (years): 12 to 18

5–8/2020

Stringency Index:

71.1 (31.5 to 79.6)

School Closure Index:

2.9 (2.0 to 3.0)

PP1: 2016–17

PP2: 2017–18

PP3: 2018–19

Same population

General anxiety symptoms

Generalised Anxiety Disorder Scale (GAD-7), moderate-to-severe anxiety as GAD-7 score ≥ 10;

Psychometric properties [79];

Self-reported

Serious

Widnall,

2022 [22]

Longitudinal 3-wave panel survey

PP: 589 (59.2)

DP1: 587 (58.8)

DP2: 587 (59.8)

Mean (years): 13.2

Age range (years): 13 to 15

DP1: 5/2020

DP2: 10/2020

DP1:

Stringency Index:

74.2 (69.4 to 79.6)

School Closure Index:

3.0 (3.0 to 3.0)

DP2:

Stringency Index:

67.9 (60.2 to 75.0)

School Closure Index:

3.0 (3.0 to 3.0)

10/2019

Same population: PP and DP1

DP2: Other population

General anxiety symptoms

Hospital Anxiety & Depression Scale (HADS), subscale anxiety;

Psychometric properties [80];

Self-reported

Serious

Wright,

2021 [36]

Cohort study, population‐based birth cohort (Wirral Child Health and Development Study)

Self-rated:

PP: 187 (46.5)

DP: 163 (45.4)

Mother-rated:

PP: 226 (45.5)

DP: 199 (54.8)

Mean (years) ± SD, 12.0 ± 0.4

Age range (years): 10 to 12

6–8/2020

Stringency Index:

67.9 (64.4 to 73.2)

School Closure Index:

2.8 (2.0 to 3.0)

12/2019—3/2020

Same population

General anxiety symptoms

Short Spence Anxiety Scale;

Psychometric properties [81];

Mother-reported

Serious

Bignardi,

2020 [55]

Cohort study, Resilience in Education and Development (RED) study

School group:

114 (49.1)

Lab group:

54 (63.0)

PP:

School group: mean (years) ± SD,

8.7 ± 0.6

Lab group: mean (years) ± SD,

8.5 ± 0.7

DP:

School group: mean (years) ± SD,

10.5 ± 0.7

Lab group: mean (years) ± SD,

9.4 ± 0.8

Age range (years): 7 to 11

4–6/2020

Stringency Index:

74.9 (67.6 to 79.6)

School Closure Index:

3.0 (3.0 to 3.0)

School group: 6/2018 to 3/2019

Laboratory group:

12/2018 to 9/2019

Same population

General anxiety symptoms

Revised Child Anxiety and Depression Scale (RCADS)-short form with anxiety subscales;

Psychometric properties [70];

PP: self/parent-reported,

DP: parent-reported

Serious