Aims Excessive crying in otherwise healthy infants, often termed infant colic, continues to be an enigmatic condition to treat. Manual therapy is an option, yet the evidence remains controversial not least because of the role of the parent in reporting the child's symptoms. The aim of this study was to compare a short course of manual therapy with no treatment, and to consider any biasing effect by the parent on the report of crying.

Methods Infants below the age of 8 weeks were randomised to one of three groups: i) infant treated, parent aware; ii) infant treated, parent unaware; iii) infant not treated, parent unaware. The primary outcome was a daily crying time diary completed by parents over a period of 10 days during which the infant was treated on a needs basis.

Results In parents blinded to treatment allocation, using conservative cut-off values to determine a clinically significant improvement in crying time, the increased odds of improvement in treated infants compared to those not receiving treatment were statistically significant at day 8 (adjusted OR 8.1 (95% CI 1.4 to 45.0)) and at day 10 (adjusted OR 11.8 (2.1 to 68.3)). The number needed to treat was 3. In contrast, the odds of improvement in treated infants were not significantly different in blinded compared to non-blinded parents (adjusted ORs 0.7 (0.2 to 2.0) and 0.5 (0.1 to 1.6) at days 8 and 10 respectively).

Conclusion These findings support a short-term effect of manual therapy that does not appear to be influenced significantly by parental reporting bias.