Sir.—Because my oldest son was a thumb-sucker who also carried a blanket and now needs orthodontic correction of malaligned teeth, I was particularly interested in the recent article by Friman.1
Thumb-sucking seems to be fairly common, yet Friman studied only eight patients. This seems like a very small sample size considering the prevalence of this problem. The eight patients who were followed up seem to have been preselected in a sense, not only because of the general inclusion criteria, but also because of the apparent motivation to stop thumbsucking exhibited by both the children and their parents. Thumbsucking, with or without other object attachment, is a very common problem. Therefore, it seems to me that Friman could have studied a much larger patient group and reached much more valid conclusions. Similar problems occur in studies in orthopedic surgery, especially those in which the natural history of a disease
LUBICKY JP. Thumb-Sucking. Am J Dis Child. 1991;145(8):845–846. doi:10.1001/archpedi.1991.02160080019005
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