Letters Section Editor: Stephen J. Lurie,
MD, PhD, Senior Editor.
To the Editor: Dr Lynskey and colleagues1 used a matched cohort design to study the association
between cannabis use by the age of 17 years with drug use later in life. Twins
who had used cannabis by the age of 17 years were matched with their sibling
who had not used cannabis by that age. This design eliminates possible confounding
by any shared genetic and environmental factors. The authors estimated odds
ratios (ORs) using conditional logistic regression.
Cummings P. Early Exposure to Marijuana and Risk of Later Drug UseEarly Exposure to Marijuana and Risk of Later Drug Use. JAMA. 2003;290(3):329. doi:10.1001/jama.290.3.329-a