September 13, 1985

Treatment of Genetic Hormonal Deficiencies by Nicotine

Author Affiliations

The Wharton School University of Pennsylvania Philadelphia

JAMA. 1985;254(10):1311-1312. doi:10.1001/jama.1985.03360100059012

To the Editor.—  It is not clear in the letters by Berman and Hogue1 and by Sexton and Hebel2 concerning the relationship between maternal cigarette smoking and infant birth weight that the authors understand that biologic causality cannot be established by statistical evidence alone.3,4 Correctly used, statistical methods can reject hypotheses, but they can never validate them.3 We noted a positive association between maternal prepregnant weight and mean birth weight and also between maternal height and mean birth weight.4 Furthermore, it was suggested4 that the arbitrary 2,500-g birth weight "break-point" criterion between presumably healthy and unhealthy infants is surely an oversimplification. If both parents are, say, 160 cm (5 ft 3 in) tall or less and weigh 58.8 kg (130 lb) or less, as compared with parents 178 cm (5 ft 10 in) tall or taller and weighing 72.3 kg (160 lb) or more,