| Study | Reason for exclusion |
|---|---|
| Andersson 1988a | Non‐randomised controlled trial |
| Antila 1962 | Non‐randomised controlled trial |
| Bender 1967 | Non‐randomised controlled trial |
| Brandfonbrener 1986 | Non‐randomised and outcome not symptom control |
| Breen 1965 | Retrospective non‐randomised |
| Evans 1960 | Non‐randomised controlled trial |
| Gordon 1968 | Non‐randomised controlled trial |
| Schumacher 1963 | Non‐randomised controlled trial |
| Simonsen 1996 | Non‐randomised controlled trial |
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