Table 1 Characteristics of included studies

Germany

Ravens-Sieberer, 2022 [42]

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 depression symptoms

Center for Epidemiological Studies Depression Scale (CES-DC), self-reported

Moderate

Witte, 2022 [46]

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

PP: 533,701 (48.6)

PP: 332,945 (48.6; stationary care)

DP1: 545,626 (48.6)

DP1: 339,361 (48.6; stationary care)

DP2: 343,642 (48.5; stationary care)

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 depression rates

Pediatric visit/ Hospitalization rate

ICD-10: F32/33,

pediatric reported

Moderate

Bujard,

2021 [29]

Cohort study, pairfam

PP: 854 (57.7)

DP: 854 (57.7)

Age range (years):

16 to 19

5–7/2020

Stringency index:

60.4 (55.1 to 63.4)

School closure index:

2.2 (1.0 to 3.0)

11/2018 to 7/2019

Same population

General depression symptoms,

Clinically relevant depression rates

German adaption of State-Trait Depression Scale (STDS),

self-reported

Moderate

Kostev,

2021 [38]

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

PP: 206,528 (39.2)

DP: 203,742 (39.7)

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 depression rates

Pediatric visit

ICD-10: F32, F33,

pediatric reported

Moderate

Rau,

2021 [41]

Cohort study

PP: 777 (53.3)

DP: 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 depression symptoms,

Clinically relevant depression rates

Revised Child Anxiety and Depression Scale (RCADS), depression subscale,

self-reported

Serious

Iceland

Thorisdottir,

2021 [44]

Longitudinal study, Youth in Iceland school surveys

PP1: 19,682 (50.1)

PP2: 18,126 (50.4)

DP: 15,725 (51.8)

Age range (years):

13 to 18

10/2020

Stringency index:

43.1 (38.0 to 52.8)

School closure index:

1.0 (1.0 to 1.0)

PP1: 2016

PP2: 2018

Same population

General depression symptoms

Symptom Checklist‐Revised (SCL‐90), subscales of depressed mood and anger, self-reported

Moderate

Halldors-dottir,

2021 [35]

Cross-sectional study, LIFECOURSE (Longitudinal Investigation For Epidemiologic Causes and OUtcomes RiSing in Early Childhood and Adolescence)

PP: 504 (43.1)

DP: 504 (43.1)

Age range (years):

16 to 17

10/2020–4/2021

Stringency index:

49.0 (40.7 to 65.7)

School closure index:

1.2 (1.0 to 3.0)

2018

Cross-sectional measure

General depression symptoms

Symptom Checklist‐Revised (SCL‐90), subscales of depressed mood and anger,

self-reported

Serious

Israel

Shoshani,

2021 [43]

2-point survey

PP: 1537 (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 depression symptoms

Brief Symptom Inventory 18 (BSI-18), subscale depression,

self-reported

Moderate

Italy

Frigerio,

2022 [33]

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,

parent-reported

Serious

Crescentini,

2020 [31]

Online survey

PP: 721 (48.4)

DP: 721 (48.4)

Mean (years) ± SD, 10.1 ± 2.5

Age range (years):

6 to18

4–5/2020

Stringency index:

90.2 (75.0 to 93.5)

School closure index:

3.0 (3.0 to 3.0)

Backward consideration (the last months of 2019)

Same population

General depression symptoms

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

parent-reported

Critical

Netherlands

Luijten,

2021 [39]

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 the same population)

General depression symptoms

Patient-Reported Outcome Measurement Information System (PROMIS), CAT V2.0-Depressive Symptoms,

self-reported

Moderate

Janssen,

2020 [36]

Cohort study, RE-PAIR study: ‘Relations and Emotions in Parent-Adolescent Interaction Research’ and

on the follow-up assessment ‘RE-PAIR during the COVID-19 pandemic

PP: 28 (64.3)

DP: 20 (65.0)

PP: Mean (years) ± SD, 16 ± 1.2

DP: Mean (years) ± SD, 17.0 ± 1.0

Age range (years):

11 to 17

4/2020

Stringency index:

78.7 (78.7 to 78.7)

School closure index:

3.0 (3.0 to 3.0)

9/2018-

11/2019

Same population

General depression symptoms

Patient Health Questionnaire (PHQ-9),

self-reported

Serious

Norway

Soest,

2022 [47]

Cross-sectional survey, Norwegian national youth survey (Ungdata)

PP1: 11,719 (49)

PP2: 24,694 (50)

PP3: 10,555 (50)

PP4: 44,103 (51)

PP5: 30,246 (50)

PP6: 8,792 (50)

PP7: 10,552 (50)

DP: 86,597 (51)

PP1: Mean (years) ± SD, 15.1 ± 1.6

PP2: Mean (years) ± SD, 15.1 ± 1.5

PP3: Mean (years) ± SD, 15.0 ± 1.5

PP4: Mean (years) ± SD, 15.3 ± 1.6

PP5: Mean (years) ± SD, 15.5 ± 1.6

PP6: Mean (years) ± SD, 15.5 ± 1.6

PP7: Mean (years) ± SD, 15.7 ± 1.6

DP: Mean (years) ± SD, 15.3 ± 1.6

total: Mean (years) ± SD, 15.3 ± 1.6

Age range (years): 13 to 18

1–3/2021

Stringency index:

68.9 (56.0 to 73.2)

School closure index:

1.7 (1.0 to 2.0)

PP1: 2014

PP2: 2015

PP3: 2016

PP4: 2017

PP5: 2018

PP6: 2019

PP7: 2020 (before 3/2020)

Cross-sectional survey

General depression symptoms

Hopkins Symptom Checklist (HSCL),

self-reported

Moderate

Burdzovic,

2021 [30]

Cohort study, MyLife study

PP: 1,335 (60.0)

DP: 741 (59.8)

School grades 10 and 11 (approx. 15 to 16 years)

10–12/2020

Stringency index:

48.1 (32.4 to 56.0)

School closure index:

1.0 (1.0 to 1.0)

2018/2019

Same population

General depression symptoms,

Clinically relevant depression rates

Patient Health Questionnaire (PHQ-9; adolescent version),

self-reported

Moderate

Myhr,

2021 [40]

Cross-sectional survey, subsample of the Norwegian national youth survey (Ungdata) in Trøndelag

County

PP: 2,126 (52.0)

DP: 1,957 (50.7)

Age range (years): 13 to 16

5/2020

Stringency index:

58.3 (58.3 to 58.3)

School closure index:

1.0 (1.0 to 1.0)

3/2020

PP: Subsample of a representative survey

DP: cross-sectional data

General depression symptoms

Hopkins Symptom Checklist (HSCL),

self-reported

Moderate

Hafstad,

2021 [34]

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 depression symptoms

Hopkins Symptom Checklist (HSCL-10),

self-reported

Serious

Switzerland

Ertanir,

2021 [32]

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 depression symptoms

Hopkins Symptoms Checklist (HSCL-25), subscale depression,

self-reported

Moderate

Borbás,

2021 [28]

Cohort study

PP: 26 (38.5)

DP: 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,

NI

Critical

United Kingdom

Knowles,

2022 [37]

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 depression symptoms

Short Mood and Feelings Questionnaire (SFMQ), depression as SMFQ score ≥ 12,

self-reported

Serious

Widnall,

2022 [45]

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

PP and DP1: Same population

DP2: Other population

General depression symptoms

Hospital Anxiety & Depression Scale (HADS),

self-reported

Serious

Wright,

2021 [21]

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 depression symptoms

Short Mood and Feelings Questionnaire (SMFQ),

self-reported and mother-reported

Serious

Bignardi,

2020 [27]

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 depression symptoms

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

PP: self/parent-reported,

DP: parent-reported

Serious