Table 1.
Summary of results.
| General characteristics | N_all (%) | N_dev (%) | DNAm and brain characteristics | N_all (%) | N_dev (%) | Additional variables examined | N_all (%) | N_dev (%) |
|---|---|---|---|---|---|---|---|---|
| Design | DNAm approach | Genetic influences | ||||||
| Cross-sectional | 94 (85%) | 13 (57%) | Candidate | 74 (67%) | 12 (52%) | No | 63 (57%) | 9 (39%) |
| Prospective/longitudinal | 17 (15%) | 10 (43%) | Genome-wide | 26 (23%) | 7 (30%) | Yes | 48 (43%) | 14 (61%) |
| Epigenetic score | 15 (14%) | 4 (17%) | ||||||
| Sample type | DNAm tissue | Environmental influences | ||||||
| Clinical | 50 (45%) | 4 (17%) | Peripheral blood | 83 (75%) | 9 (39%) | No | 83 (75%) | 10 (43%) |
| Population/Cohort study | 29 (26%) | 8 (35%) | Saliva | 23 (21%) | 11 (48%) | Yes | 28 (25%) | 13 (57%) |
| High-risk | 20 (18%) | 9 (39%) | Cord blood/tissue | 5 (5%) | 5 (22%) | Of which: | ||
| Genetically-informed (e.g. twin, pedigree) | 4 (4%) | 2 (9%) | Buccal | 5 (5%) | 1 (4%) | Psychological | 23 (82%) | 11 (85%) |
| Other (e.g. convenience, community) | 11 (10%) | 0 (0%) | Brain (postmortem) | 3 (3%) | – | Physiological | 5 (18%) | 2 (15%) |
| Developmental period | Most investigated candidate genes (>4 studies; n = 51) | Biological markers | ||||||
| Adulthood | 85 (77%) | – | SLC6A4 | 17 (15%) | 5 (22%) | No | 94 (85%) | 20 (87%) |
| Adolescence | 16 (14%) | 16 (70%) | OXT/R | 12 (11%) | 3 (13%) | Yes | 17 (15%) | 3 (13%) |
| Neonatal | 6 (5%) | 6 (26%) | FKBP5 | 11 (10%) | 1 (4%) | Of which: | ||
| Old age | 8 (7%) | – | NR3C1 | 6 (5%) | – | mRNA/gene expression levels | 12 (71%) | 2 (67%) |
| Childhood | 6 (5%) | 6 (26%) | BDNF | 6 (5%) | 1 (4%) | Protein levels and metabolomics | 7 (41%) | 1 (33%) |
| Postmortem | 2 (2%) | – | ||||||
| Repeated measures | Neuroimaging modality | Psychiatric and behavioral outcomes | ||||||
| No | 103 (93%) | 20 (87%) | structural MRI | 53 (48%) | 13 (57%) | No | 28 (25%) | 10 (43%) |
| Yes | 8 (7%) | 3 (13%) | task-based fMRI | 39 (35%) | 5 (22%) | Yes | 83 (75%) | 13 (57%) |
| Of which: | diffusion MRI | 21 (19%) | 6 (26%) | Of which: | ||||
| Repeated DNAm | 3 (38%) | 2 (66%) | resting-state fMRI | 8 (7%) | 2 (9%) | Depression and anxiety | 25 (30%) | 6 (26%) |
| Repeated neuroimaging | 6 (75%) | 2 (66%) | PET | 6 (5%) | – | Psychotic disorders | 20 (24%) | 2 (9%) |
| Neurodegenerative and ageing-related | 7 (8%) | – | ||||||
| Post-traumatic stress disorder | 8 (10%) | – | ||||||
| Replication | Neuroimaging approach | Attention deficit hyperactivity disorder | 3 (4%) | 1 (4%) | ||||
| No | 100 (99%) | 18 (78%) | Region of Interest (ROI) | 74 (67%) | 16 (70%) | Cognitive and social processes | 11 (13%) | 2 (9%) |
| Yes | 11 (10%) | 5 (22%) | Voxel-/ vertex-wise | 44 (40%) | 8 (35%) | Substance use and addiction | 7 (8%) | 1 (4%) |
| Global | 14 (13%) | 2 (9%) | Other | 4 (5%) | 1 (4%) | |||
Some categories may add up to more than 100% due to certain studies meeting multiple criteria at once (e.g. studies investigating multiple tissues or multiple biological markers). N_all = N for all periods; N_dev = N for the developmental period (<18 years).