SAN RAFAEL, Calif. — Public health officials say marijuana addiction is on the rise, possibly because of the increasing potency of genetically engineered plants and the use of concentrated products, or because more users are using the drug several times a day
Addiction to the drug is not new but a well-defined disorder that includes physical withdrawal symptoms, cravings, and psychological dependence.
‘‘There should be no controversy about the existence of marijuana addiction,’’ said David Smith, a physician who has been treating addiction since he opened a free clinic in San Francisco’s drug-drenched Haight-Ashbury neighborhood in the 1960s.
‘‘We see it every day,’’ Smith said. “The controversy should be why it appears to be affecting more people.’’
Although estimates of the number of people who use marijuana vary, the federal government and the marijuana industry tend to agree that total marijuana use has remained relatively constant over the past decade.
Increased use in the past three years has been slight, despite increased commercial availability in states that have legalized it.
The percentage of people who become addicted to marijuana — estimated at about 9 percent of all users, and about 17 percent of those who start in adolescence — also has been stable. Some studies report that even higher proportions of marijuana users develop a dependence, which means they experience withdrawal symptoms when they stop using the drug.
Yet here in Northern California, some addiction treatment practitioners say they’re seeing a surge in demand for help, particularly among adolescents.
Marijuana’s estimated rate of addiction is lower than that of cocaine and alcohol (15 percent) and heroin (24 percent). Unlike with opioids and stimulants, marijuana dependence tends to develop slowly: Months or years may pass before symptoms begin to affect a dependent user’s life.
There are no known reports of anyone dying of a marijuana overdose or of the drug’s common withdrawal symptoms: chills, sweats, cravings, insomnia, loss of appetite, nausea, anxiety, and irritability.
According to Nora Volkow, director of the National Institute on Drug Abuse, an estimated 2.7 million Americans meet the diagnostic criteria for marijuana dependence, second only to alcohol dependence.
Smith, a visiting physician at Muir Wood Adolescent and Family Services, a treatment center for boys, speculates that the potency of today’s marijuana is causing a higher prevalence of problematic marijuana use.
‘‘Back in the day when kids were sitting around smoking a joint, the THC levels found in marijuana averaged from 2 to 4 percent,’’ Smith said. ‘‘That’s what most parents think is going on today. And that’s why society thinks marijuana is harmless.’’
But selective breeding has resulted in an average potency of 20 percent THC, the primary psychoactive compound in marijuana. Some strains exceed 30 percent.
Marijuana concentrates and extracts, much more commonly used in the past five years, have THC levels that range from 40 percent to more than 80 percent, according to marijuana industry promotional information and Drug Enforcement Administration reports.