*The following is excerpted from an online article posted on HealthDay.
Pot's increasing potency could make it more likely that toking will interfere with users' lives, a new study argues.
Compared to pot of the 1990s, today's marijuana contains significantly higher levels of THC, the chemical compound that causes intoxication, the research team notes.
This added punch may be associated with an higher risk of cannabis use disorder, researchers from the University of Michigan and Brown University conclude.
They said the THC concentration of pot confiscated by the U.S. Drug Enforcement Agency has increased steadily from 3.5 percent in 1994 up to 12.3 percent in 2012.
Meanwhile, average risk of developing cannabis use disorder increased by about 40 percent with every 1 percentage point increase in national pot potency, they found.
"It definitely is a signal that potency increases the addictive potential of cannabis," said senior author Brian Hicks, an associate professor with the University of Michigan Addiction Center. And there are no laws regarding potency, he added.
States with legal marijuana might want to hone their laws to make THC levels in pot products clearer for consumers, just as alcohol levels are displayed on liquor bottles, the researchers said. Currently, 10 states and Washington, D.C., allow recreational marijuana use and many more states allow medical use.
"We really need to look at the idea of regulating potency levels, and examining how potency relates to things you'd care about, like ability to drive and addiction potential," Hicks said.
"Levels have really gone up the last five years," particularly in pot products such as edibles and concentrates, he added.
In the new study, Hicks and his colleagues compared federal statistics on pot potency with data gathered on participants in the Michigan Longitudinal Study. That's an ongoing research project focused on families at increased risk for substance abuse disorders.
They specifically looked for symptoms related to cannabis use disorder, a condition recognized by the American Psychiatric Association. These symptoms might include an inability to cut down or control cannabis use, failing to meet obligations due to pot use, or using the drug even in physically hazardous situations, Hicks said.
The researchers found that regular pot users who first tried marijuana when national average THC levels held at 4.9 percent had almost twice the increased risk of developing symptoms of cannabis use disorder within a year.
But those who started regularly using pot when national average THC levels were 12.3 percent had a 4.8 times higher risk of cannabis use disorder.
The study is "one of the first to show increased risk of progression to cannabis use disorder with higher potency marijuana," said Dr. Scott Krakower, assistant unit chief of psychiatry with Zucker Hillside Hospital in Glen Oaks, N.Y.
The new study appeared in Drug and Alcohol Dependence.