Contrasting Models of Genetic Co-Morbidity For Cannabis and Other Illicit Drugs in Adult Australian Twins
Agrawal A et al., "Contrasting models of genetic co-morbidity for cannabis and other illicit drugs in adult Australian twins," Psychological Medicine 37, issue 1 (January 2007): 49-60.
In this examination of the gateway theory, researchers studied more than 4,000 Australian twins whose use of marijuana and other drugs was followed in detail from adolescence into adulthood and matched the real-world data from the twins to mathematical models based on 13 different explanations of how use of marijuana and other illicit drugs might be related. The scientists concluded the data don't show that marijuana causes use of other drugs, but instead indicate that the same factors that make people likely to try marijuana also make them likely to try other substances.
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