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July 16, 2003

Early Exposure to Marijuana and Risk of Later Drug UseEarly Exposure to Marijuana and Risk of Later Drug Use

Author Affiliations

Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2003;290(3):330. doi:10.1001/jama.290.3.330-a

To the Editor: In her Editorial about the possible causal mechanisms of drug addiction, Dr Kandel1 did not discuss the risk associated with prenatal administration of opiates or sedatives. Several studies2-4 have found that administration of these drugs during labor is a risk factor for later addiction in adolescence or adulthood. Not only have these studies found a dose-response relationship between drug exposure and subsequent risk of drug addiction, but also have the advantage that the perinatal drug exposure is limited to a few hours during birth. This restricts the range of confounding factors (eg, socioeconomic status or residential environment5,6) that can possibly moderate this long-term effect. Since any drug administered prenatally would be expected to cross the placenta about equally to twin fetuses irrespective of whether they are monozygotic or dizygotic twins, such an explanation is consistent with the observation that no differences were found between these 2 categories of twins in the recent study by Lynskey et al.7 Epidemiological studies that do not assess or control for proximate factors on subsequent drug addiction may have a limited ability to examine the effects of other causal factors occurring later in the drug addict's life.