In Reply: Dr Anand raises 2 issues in epidemiological
research on the etiology of substance abuse.
First, he suggests that the models tested by Lynskey et al1 were
misspecified. Assuming that administration of opiates or other drugs to mothers
at the time of delivery does increase the risk of drug addiction in offspring,
does the omission of this factor in the analysis of Lynskey et al affect their
conclusions in any way? I agree with Anand that the conclusions of Lynskey
et al are not invalidated by the lack of attention to perinatal exposure to
obstetric pain medication at the time of delivery. Both twins were similarly
exposed to the putative perinatal causal factor. In a twin design, perinatal
experiences are part of the shared influences that are held constant for subjects.
Kandel DB. Early Exposure to Marijuana and Risk of Later Drug Use—Reply. JAMA. 2003;290(3):331–332. doi:10.1001/jama.290.3.331
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