"Beginning marijuana use at a young age has been linked with negative cognitive and behavioral consequences," said Natasha Sokol, who led the study while a doctoral student at Harvard Chan School and is now a postdoctoral research fellow at Brown University School of Public Health's Center for Alcohol and Addiction Studies.
‘Children whose mothers use pot are more likely to start using drugs earlier compared to children whose mothers do not use marijuana.’
"In a shifting regulatory environment in the U.S. in which the visibility and acceptability of adult marijuana use are expected to increase, it's important to understand better how these changes may impact children's early marijuana use so that we can better identify at-risk youth and implement effective prevention strategies."
Prohibiting marijuana isn't necessarily consistent with public health goals, according to the study authors. For example, marijuana has recognized therapeutic benefits for a number of health conditions and may serve as a safer alternative to opioids. In addition, more than half of all drug arrests in the U.S. are marijuana-related and are a major driver of racial disparities in arrest and incarceration.
But in children who begin use at a young age, marijuana has been linked with negative consequences such as impairments in concentration and decision-making, increased impulsivity, and reductions in IQ. The younger a child is when he or she begins using marijuana, the more severe the effects, studies have suggested.
Therefore, delaying marijuana initiation may be an important public health goal, the authors said.
Using data from the National Longitudinal Survey of Youth 1979 and Child and Young Adults, the new study assessed the timing and extent of marijuana use and initiation among 4,440 children and 2,586 mothers. Researchers tested for the effect of a mother's marijuana use between a child's birth and age 12 on that child's subsequent risk of marijuana initiation, controlling for factors related to the child's early life behavior and cognition and on the family's socioeconomic position and social environment.
The study found that 2,983 children (67.2%) and 1,053 mothers (35.3%) self-identified as marijuana users. Children whose mothers used marijuana were at increased risk for starting marijuana use prior to age 17, and they began using at a median age of 16, compared with age 18 for children whose mothers didn't use the drug. The association was slightly stronger among non-Hispanic non-black children.
One limitation of the study was that it did not measure whether children were aware of their mothers' marijuana use. The study also lacked data on the frequency and severity of mothers' marijuana use.
"Although more research is needed, physicians who prescribe marijuana might consider educating parents who use the drug about the potential dangers of early marijuana use among their children, and provide information and preventive strategies to delay such use," said Vaughan Rees, lecturer on social and behavioral sciences and director of Harvard Chan School's Center for Global Tobacco Control.