Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Correlation between self-reported past 30-day frequency of marijuana use and quantified THC-COOH umbilical cord homogenate assay results. Reported values for THC-COOH are in ng/g. Spearman’s correlation coefficient is reported with 95% confidence intervals.
