Letters Section Editor: Stephen J. Lurie,
MD, PhD, Senior Editor.
To the Editor: Dr Lynskey and colleagues1 interpreted their data as providing evidence that
cannabis use caused subsequent drug problems through a "gateway" effect.
This study, however, may have been subject to various biases that would
negate this interpretation. For example, drug use and problems were measured
via uncorroborated self-report, which can be unreliable.2 Different
individuals, due mainly to different perceptions of social desirability, may
tend to either underreport or overreport their experience of drug use and
drug problems. Such reporting tendency would generate a spurious association
between use of and problems with one drug and use of and problems with another.
The importance of the issue of reporting bias may have been generally underestimated
in observational epidemiology.3
Macleod J, Hickman M, Smith GD. Early Exposure to Marijuana and Risk of Later Drug Use. JAMA. 2003;290(3):329-330. doi:10.1001/jama.290.3.329-a