| Study | Reason for exclusion |
|---|---|
| Benton 1978 | No control group |
| Bezan 1988 | Survey, no control group |
| Danis 2000 | Non‐randomised cohort study |
| Eime 2004 | Interview survey, no control group |
| Forst 2006 | Cohort study, no control group, observational |
| Mancini 2005 | No distinct control group |
| Murthy 1994 | Uncontrolled before and after study |
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