Response: Re: A Randomized, Controlled Trial of a Behavioral Intervention to Reduce Crying among Infants

To the Editor: We appreciate the thoughtful letter written by Dr. Karp¹ in response to the recent randomized controlled trial of The Happiest Baby on the Block (THB) video techniques,² a proprietary program which he has designed.³

We find his critiques mostly fair and fully acknowledged in our publication. Early trials of new interventions are often small and subject to the risk of a type II error. However, small trials can help identify unforeseen consequences and determine the appropriate sample size for larger trials. The only significant finding of the article was that mothers in the intervention group reported more stress at 12 weeks compared with parents in the control group (P = .01).² There was a tendency toward more crying by the babies in the intervention group at every time point (ie, P = .04 at 8 weeks), but this did not reach our a priori level of statistical significance.² Given that this study showed more crying at every time point maong babies whose mothers received the THB video intervention, these findings are not useful for supporting a larger trial of THB techniques as delivered.

A drop out rate of 30% is a concern, but not out of the ordinary. We did compare participants that remained to those that dropped out and found little important difference.

We are puzzled by Dr. Karp's concern about contamination. We did not advise mothers in the control group to swaddle their babies. Many mothers in both groups reported the use of swaddling, bouncing, swinging, and pacifiers to calm their babies. It is possible that an intervention such as THB technique will be of little use if such behaviors are either culturally normative or hard wired.

We appreciate Dr. Karp's concern about the lack of “use” of the intervention. This is akin to the ever-present challenge of nonadherence. In the real world, people who pick up a copy of THB book or video either read it/watch it or not, and the either use it or not. Given that the program's website reports that more than 350,000 copies have been sold,³ it seems time to test the effectiveness of a limited intervention. It is plausible that training educators to work with families may be more useful. We are impressed that more than 2000 certified educators have been trained. We hope that this technique is rigorously evaluated.

We applaud the ongoing research of THB techniques. None of the citations provided by Dr. Karp are available in the peer-reviewed literature. The Department of Public Health program has an extended abstract available.⁴ This is a small intervention that serves as an add-on to an existing home visiting program. There is no appropriate comparison group. It is likely that the babies in the intervention group started to cry less as they aged (like all babies) and their parents gained confidence in parenting as they gained experience. Dr. Karp's claim of an “immediate, dramatic, and continuing improvement in ability to calm a crying infant” is not supported by available study documentation, and the methods used for measurement are not reported. There are no available details regarding the randomized controlled trial that was funded by the National Institute of Health.

The University of Arizona survey is only available at the THB website. The education and analytic methods are poorly described. This report presents the response of parents in classroom settings who were given a survey of questions before and after implementation of the techniques that was designed to illicit positive change from the material presented.⁵

In short, although we agree with most of the limitations presented by Dr. Karp, we believe that our study and the peer-reviewed publication in this journal represent a significant addition to the quality of literature available to assess the effectiveness of the THB program. We look forward to future, rigorous, peer-reviewed studies of the THB program.