Study quality assessed by the Newcastle-Ottawa Scale
| Study | Paper | Representativeness of sample | Sample size | Non-respondents | Ascertainment of exposure | Comparability | Outcome | Statistical test | Length of follow-up | Adequacy of follow-up | Total | |
| 0–2 | 0–1 | 0–1 | 0–1 | 0–2 | 0–2 | 0–1 | 0–1 | 0–1 | 10 | 12 | ||
| 1 | Chenery25 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | – | – | 8 | – |
| 2 | Coole et al 26 | 1 | 0 | 0 | 1 | 0 | 2 | 0 | – | – | 4 | – |
| 3 | Hussey et al 27 | 1 | 1 | 0 | 1 | 1 | 2 | 1 | ||||
| 4 | Coole et al GPs*28 | 1 | 0 | 0 | 1 | 0 | 2 | 0 | – | – | 4 | – |
| 5 | Coole et al RTW*30 | 1 | 1 | 0 | 1 | 0 | 2 | 0 | – | – | 5 | – |
| 6 | Shiels et al 31 | 2 | 1 | 1 | 1 | 2 | 2 | 1 | 1 | 1 | – | 12 |
| Shiels et al 32 | 2 | 1 | 1 | 1 | 2 | 2 | 1 | – | – | 10 | – | |
| Gabbay et al 33 | 1 | 1 | 1 | 1 | 2 | 2 | 1 | 1 | 1 | – | 11 | |
| Gabbay et al 34 | 1 | 1 | 1 | 1 | 2 | 2 | 1 | – | – | 9 | ||
| Shiels et al 35 | 1 | 1 | 1 | 1 | 2 | 2 | 1 | – | – | 9 | – | |
| Gabbay et al 36 | 2 | 1 | 1 | 1 | 2 | 2 | 1 | – | – | 10 | – | |
| 7 | Digital NHS37 | 2 | 1 | 0 | 1 | 2 | 2 | 0 | 1 | 1 | – | 10 |
*Study 5 by Coole et al 29 contains studies 4 and 6.
GP, general practitioner; NHS, National Health Service; RTW, return to work.