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.
The second issue is how important a risk factor for drug addiction in offspring is giving drugs to mothers at the time of delivery. The evidence cited by Anand consists of the data from 3 case-control studies.2 - 4 In the absence of further replications and of data from representative population samples, it is difficult to evaluate the effect of obstetric pain medication administered to a mother on subsequent substance use or abuse by offspring compared with that of other risk factors. Furthermore, exposure to opiates at the time of delivery may be a less important pregnancy-related risk factor than prolonged in utero exposure to maternal consumption of legal and illegal drugs in pregnancy. For instance, in utero exposure to maternal smoking has been linked to increased risk of offspring smoking in adolescence5 and of substance abuse disorders in early adulthood.6
Moreover, my goal was not to identify all the potential determinants of the use or abuse of illicit substances other than marijuana, but rather to consider the strengths and weaknesses of various strategies for determining whether marijuana use has a truly causal role in the progression to the use of other illicit drugs.
Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature
Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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