In an analysis it terms preliminary, the Washington State Institute for Public Policy reports that data offer no evidence that increasing levels of legal marijuana sales in the state have affected marijuana treatment admission rates or youth use rates.
The institute's second mandated analysis of impacts from the state's voter-approved recreational marijuana initiative (I-502) did find evidence that in counties with higher levels of legal cannabis sales, adults ages 21 and older engaged in more past-month marijuana use and more instances of heavy use.
Past-month use in these high-sale counties was actually lower in the under-21 population, a finding that researchers speculated might result from a reduction in black market supply of the drug due to emerging competition.
The researchers reported that overall use of marijuana among adults in the state has been trending upward in recent years, but they added in their report, “We have not yet addressed the question of whether these trends are caused by I-502.”
They added, “The most current outcome data available reflect the first two years of legal cannabis sales, and the supply system is still growing. In upcoming reports we will update these analyses as more current data become available and report findings from new analyses to address other of our study requirements.”
The institute conducted a between-state analysis of treatment admission data based on information from the national Treatment Episode Data Set (TEDS). This was done to compare treatment admissions in states that did and did not legalize marijuana, offering an estimate of what would have happened with admissions in Washington had marijuana not been legalized.
This analysis led to the conclusion that there were no meaningful differences in treatment admissions for marijuana use between Washington and comparison states. “That is, although admissions to substance abuse treatment for cannabis abuse fell as a percentage of all admissions in Washington in recent years, there is no evidence that the enactment of I-502 caused this change,” the report states.
In other youth-related findings, the report concluded that there was no evidence that the level of legal marijuana sales has affected a number of indicators of youth marijuana use in grades 8, 10 and 12.