The murky DAWN

It’s that time again — it’s DAWN — the Drug Abuse Warning Network. Their latest report is out, and as the results are manipulated and analyzed, you’ll start to hear dire reports in the media about how some drug or another is particularly of concern in connection to emergency room visits.
The full 80 page pdf report is available here (Thanks to The Drug Update for the link).
You need to go to page 61 of the report to really understand how this works.

Under the current methodological design, medical charts for all ED visits within the selected hospitals are reviewed retrospectively to find the drug-related cases for submission to DAWN. DAWN includes ED visits associated with substance abuse and drug misuse, both intentional and accidental. DAWN also includes ED visits related to the use of drugs for legitimate therapeutic purposes. To be a DAWN case, a drug needs only to be implicated in the visit; the drug does not need to have caused the visit. Only recent drug use is included; the reason a patient used the drug is irrelevant, and the case criteria are broad enough to encompass all types of drug-related events, which include, but are not limited to, explicit drug abuse. This approach, which finds ED visits related to drug abuse only indirectly, recognizes that medical records (the source of DAWN data) frequently lack explicit documentation of substance abuse, and distinctions between use, misuse, and abuse of drugs are often subjective.
DAWN uses the data from the visits classified as DAWN cases in the selected hospitals to calculate various estimates of drug-related visits for the Nation as a whole, as well as for specific metropolitan areas. To calculate these estimates and measure their precision, the DAWN survey requires the application of sampling and weighting
methodologies. [emphasis added]

It then goes on for seven pages to describe how the results are tweaked in the attempt to provide representative data based on the hospitals that were selected.
Now it’s possible that there is useful information that can somehow be gained from such an analysis.
However, unlike the conclusions sometimes drawn in news reports, what DAWN does NOT demonstrate is any connection between the use of a drug and the likelihood that it will send you to the emergency room.