SAN RAFAEL, Calif. — For as long as most residents can remember, smoking marijuana has been a part of life here. The fact that California legalized the practice in January went practically unnoticed in this quiet town a half-hour’s drive north of San Francisco, where some say the normalization of America’s marijuana culture got its start.

For Quintin Pohl and other teenagers before him, smoking pot was a rite of passage. It was a diversion from the loneliness he felt at home when his parents were splitting up and a salve for middle-school angst. It was his entire social life in seventh and eighth grades, he said, when social life is everything.

Even though nearly all his friends were using marijuana and seeming to enjoy it, Pohl said, at some point his marijuana use took a turn he never saw coming: He became addicted.

Many people are unaware of marijuana addiction. But in the public health and medical communities, it is a well-defined disorder that includes physical withdrawal symptoms, cravings and psychological dependence. Many say it is on the rise, perhaps because of the increasing potency of genetically engineered plants and the use of concentrated products, or because more users are partaking multiple times a day.

“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. 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 where Pohl eventually got help, speculates that the potency of today’s pot 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.

Susan Weiss, who directs research on the health effects of marijuana at the National Institute on Drug Abuse, told a group of addiction doctors at the annual meeting of the American Society of Addiction Medicine in April that the federal government is trying to get the message out that marijuana can be addictive.

“But believe it or not,” she told the group, “we’re having a hard time convincing people that addiction exists.”

The National Cannabis Industry Association’s chief spokesman, Morgan Fox, said he’s not surprised the federal government is having a hard time convincing the public that marijuana can be addictive.

“It’s their own fault,” he said of the government. “When people find out they’ve been lied to by the federal government about the relative harms of marijuana for decades, they are much less likely to believe anything they have to say going forward, even if that information is accurate.”

Fox said his organization has no disagreement with the finding that about 9 percent of people who use marijuana become addicted, and his organization urges its members to make that clear in their marketing information. But he disagrees that more-potent forms of marijuana may be causing an increase in addiction. “It just means people need to consume less to achieve the desired effect,” he said.

So far, no scientific studies have shown that stronger pot increases the likelihood of addiction, and large swaths of the general public continue to question the existence of marijuana addiction. But for Quintin Pohl, addiction was real.

Pohl said his marijuana addiction took years to develop. His mother, Kimberly Thomas, said that once she realized her son was using marijuana frequently, “it was like a roller coaster chugging uphill, chugging, chugging, chugging. You know something is happening,” she said, “and then just within a couple of days, you reach the peak and zoom downhill. It was awful, awful.”

Scott Sowle, executive director of the Muir Wood rehabilitation center, said he gets the same call from parents nearly every day.

“They call and say, ‘My 16-year-old son was doing really well in school. He was interested in sports and involved in extracurricular activities. But suddenly, he’s just not the same kid anymore.’ ”

Pohl recalled that he drank a little, off and on, but that marijuana was his constant obsession. After middle school, he got involved in rowing for a couple of years and took a break from his group of marijuana friends. But after he decided competitive rowing wasn’t for him, Pohl said he started smoking pot again, this time with new friends who smoked all the time.

And then the roller coaster plunged.

His grades plummeted. He stopped going home most of the time and was couch surfing for a while. Finally, he said, his mom called the police on him for stealing her car. “At that point, I was heartless, emotionless,” he said. “I was just kind of a blob taking up space. I was baked 24/7.”

Pohl’s mother said she saw that he was in trouble and demanded that he stay at home every moment he wasn’t in school. (Pohl’s father was living in San Francisco.)

“She told me to come back home. So I did,” Pohl said. “At the time, I wasn’t sure why she did that. I was still in that whole miserable phase, smoking at least an ounce of weed a week — two ounces on a good week.” (One ounce is enough to smoke four to eight joints every day for a week, depending on their size.)

Then early one morning before school, Pohl recalled, two private investigators his mother had hired appeared and took him to Muir Wood.

Pohl said he went through a week of pure misery at the rehab center: angry, in denial and suffering. “I couldn’t sleep for a week. I was cold, and then I was sweating. I hated everything,” he said. “And then the sun hit my face one morning, and it felt great. Things tasted good, smelled better, everything was just enhanced.”

During his six weeks there, Pohl took intensive classes with about 10 other boys and talked to his therapist frequently. His mother spent eight hours a week there, attending parent classes, sharing meals with her son and working with him and his therapist to address the underlying issues that had led him to self-medicate with marijuana.

Pohl says he hasn’t smoked marijuana since he left Muir Wood last July. For the rest of the summer and after school in the fall, he attended classes at a Muir Wood outpatient clinic in San Rafael.

Wearing black pants, a black sweatshirt and a pink skull cap on a cool but sunny day in late May, Pohl smiles broadly when he talks about his future. After his June graduation, he says, he plans to start working full time at the grocery store where he’s had a part-time job for the last year.

He’s thinks he can start smoking marijuana again some day — socially, when he’s an adult.

Vestal is a reporter for Stateline, an initiative of the Pew Charitable Trusts.