THURSDAY, Aug. 16, 2012 (HealthDay News) -- New high-potency marijuana and synthetic "weed" can interfere with early brain formation in developing fetuses, according to a new study, and many pregnant women may be unaware of the heightened risk.
Harmful effects of psychoactive chemicals in marijuana now on the market can begin as early as two weeks after conception, the study found. This is particularly troubling as marijuana is the most widely used illicit drug among pregnant women, the researchers say.
The study was published online Aug. 13 in Drug Testing and Analysis.
"The emergence of bioengineered crops and novel, medicinal marijuana strains, means that marijuana is no longer what it used to be in the 1970s and early 1980s," said study co-author Delphine Psychoyos, at the Center for Genetic and Environmental Medicine at Texas A&M University, in a journal news release.
"Some new, high-potency strains, including some medicinal marijuana blends, contain up to 20 times more THC, the psychoactive constituent of marijuana, than did 'traditional' marijuana'" from decades past, Psychoyos said.
Easy access to drugs via the Internet or dispensaries makes the problem worse, she added.
Exposure to latter-day versions of marijuana in early pregnancy is associated with anencephaly, a devastating birth defect in which infants are born without large parts of their brain or skull, the study found.
The study also tied early prenatal use of these drugs to attention-deficit/hyperactivity disorder (ADHD), learning disabilities and memory problems in toddlers and 10-year- olds, as well as depression, aggression and anxiety in teens.
To reach their conclusions, study authors reviewed current data on the effect of these chemicals during the earliest stages of development of the central nervous system in fetuses.
Many parenting and pregnancy websites and pro-marijuana advocacy groups base their views on marijuana on data collected prior to 1997, before the emergence of new and bioengineered marijuana strains, such as Spice products, the researchers said.
So-called synthetic marijuana or "fake weed" mixtures contain "synthetic cannabinoids" that are 500 to 600 times more potent than marijuana's THC, according to the release.
High-potency marijuana could also pose a risk to teens and young adults.
"Marijuana has regained its popularity from the 1970s, especially among teens and young people, and has established social and cultural status as the most popular drug of abuse," Psychoyos said. "Yet, like pregnant women, these young users probably have no idea of the significant increase in potency over the past four decades."
The researchers called on the U.S. government to revise policy on marijuana based on the development of synthetic cannabinoids.
The U.S. National Institutes of Health has more about substance abuse during pregnancy.