People who smoke cannabis heavily in their youth end up worse off than their parents both economically and socially, a new study finds.
The study doesn't prove cause and effect, but it does suggest that people who do use marijuana on most days end up worse off than people who don't — and it suggests that it's not their family situation that's causing their decline.
"Our study found that regular cannabis users experienced downward social mobility and more financial problems such as troubles with debt and cash flow than those who did not report such persistent use," said Magdalena Cerdá at the University of California, Davis Health System, who led the study team.
"Regular long-term users also had more antisocial behaviors at work, such as stealing money or lying to get a job, and experienced more relationship problems, such as intimate partner violence and controlling abuse."
The team studied people from Dunedin, New Zealand, who have been volunteering in a lifelong study since they were born in 1972 and 1973. More than 950 of the original 1,037 volunteers filled out questionnaires on marijuana use.
Eighteen percent, or 173 of the people, were designated marijuana dependent at one point of the study at least and 15 percent were regular cannabis users.
By the time they were 38, the volunteers who had been diagnosed as dependent on marijuana at any previous time ended up lower on the socioeconomic scale than their parents, the team reported in the journal Clinical Psychological Science.
New Zealand has a six-point occupation scale and the heavy users were, on average, about a third of a point lower on the scale if diagnosed once; they were nearly 0.8 of a point lower if diagnosed three or more times.
Those who didn't use marijuana ended up a little better off than their parents.
"On average, persistent cannabis users from middle-class origins attained lower adult socioeconomic status than did their parents, even after we controlled for sex, ethnicity, family substance-dependence history, childhood self-control, childhood IQ, history of psychopathology, achievement orientation and adult family structure," the researchers wrote.
They had more financial struggles, reported more conflict in their relationships and had more trouble at work, too.
"Our research does not support arguments for or against cannabis legalization," said Cerdá, "But it does show that cannabis was not safe for the long-term users tracked in our study."
And the illegal status of marijuana did not appear to be a factor, either, the researchers said.
"These findings did not arise because cannabis users were prosecuted and had a criminal record," said Avshalom Caspi of Duke University, who worked on the study. "Even among cannabis users who were never convicted for a cannabis offense, we found that persistent and regular cannabis use was linked to economic and social problems."