By Aaron Miller-
U.S researchers have established a link between using cannabis during pregnancy and anxiety and agression in children.
Reearchers examined 322 mother-child pairs based in New York City who were part of a wider research project on stress in pregnancy. When the children were between 3 and 6 years old, hormone levels were measured from hair samples, electrocardiogram recordings were used to measure heart function, and behavioral and emotional functioning was assessed based on parental surveys.
The researching team also looked at placental tissue collected at the time of birth for some of the participants, concluding the role of cannabis consumption by pregnant women in influencing anxiety in children.
“This new study supports a growing body of evidence that smoking cannabis during pregnancy is associated with adverse outcomes for women and their children,” Dr. Daghni Rajasingam, consultant obstetrician and spokesperson for the Royal College of Obstetricians and Gynaecologists in the United Kingdom, told the Science Media Centre in London.
“We know from previous studies that using cannabis during pregnancy is linked to impaired fetal brain development, stillbirth, low birth weight, and pre-term birth. This new evidence adds to these existing safety concerns, suggesting that cannabis use in pregnancy could lead to higher anxiety, aggression, hyperactivity, and levels of the stress hormone cortisol in the children,” she said.
“There is only a small sample of women and children used in this study, and we would like to see more research done in this area.”
According to the researchers, children of mothers who used cannabis during pregnancy showed higher anxiety, aggression, hyperactivity and levels of the stress hormone cortisol, compared with children of mothers who did not use cannabis during pregnancy, the study found.
The analysis of the placental tissue, which involved sequencing RNA molecules similar to DNA that are part of the genetic code revealed that maternal cannabis use was associated with lower expression of immune-activating genes, including cytokines, which are involved in protecting against pathogens.
“This is a well-designed study, with good methodology, and laboratory design with follow up of children. It is interesting that they were able to look at placenta signalling and link those findings with childhood outcomes,” said Dr. Darine El-Chaâr, a maternal fetal medicine specialist and clinical investigator at Ottawa Hospital Research Institute in Canada, who was not involved in the research.
The findings of one such study, published on November 15 in the Proceedings of the National Academy of Sciences USA, revealed symptoms of increased anxiety, hyperactivity and aggression in children whose parents used cannabis during pregnancy. Its analysis of placental tissue points to changes in the activity of immunity-related genes.
Today pregnant people “are being bombarded with a lot of ads to treat nausea and anxiety during pregnancy” with cannabis, the paper’s senior author Yasmin Hurd, director of the Addiction Institute at Mount Sinai said “Our studies are about empowering them with knowledge and education so that they can make decisions.”
The results are “very striking, very much a first,” says Daniele Piomelli, a professor and director of the Center for the Study of Cannabis at the University of California, Irvine, who was not involved in the work.
Pregnancy studies in rodents and even in sheep that possess a placenta similar to humans have required cautious interpretations of findings that show effects on offspring behavior and function, he says.
The new study is one of the first to tackle the question in people “in a systematic way,” Piomelli adds.
Heart Rate
Recordings of their heart-rate variability between the ages of three and six, alongside evaluations for anxiety, aggression and hyperactivitywere used to establish stress indicators. The researchers used statistical methods to exclude effects from cigarette smoking, parental anxiety and other factors that could confuse associations with cannabis use.
In the placental tissues, gene activity was altered with cannabis exposure during pregnancy: genes related to the inflammatory response showed decreased function.
Anxiety and hyperactivity levels were found to be higher in children from cannabis-exposed pregnancies, and were associated with the placental gene patterns. The researchers speculated that a decline in the activity of immune-related genes in the placenta might explain the behavioral findings.
“We always have to interpret human studies with a grain of salt,” Piomelli says, because factors other than cannabis could still be the true cause of the behavioral outcomes, including experiences after birth. Although the researchers in this study “did a really good job” of controlling for these factors, he says, “there is only so much one can do.”
Anxiety is an example of a potential confounding factor, says Mitch Earleywine, a professor of psychology at the University at Albany, State University of New York, who was not involved in the study.
The report confirms that anxiety can easily be inherited due to the lifestyle of parents, but this can also be influenced by other factors besides cannabis.
“I’m not sure that cannabis is really the issue” instead of genetics. Earleywine is also an advisory board member of the National Organization for the Reform of Marijuana Laws (NORML), which advocates for the legalization of cannabis.
Hurd agrees that human studies will always involve elements that can muddy the findings. “Yes, genetics plays a role, maternal anxiety plays a role, their postnatal environment plays a role,” she says. But even with all of that, the associations her group found with cannabis are results that “I don’t think we can ignore.”
Parents who used cannabis during pregnancy are quite concerned about the findings of the report, but Piomelli says: “the human organism is very resilient,” Piomelli says. “Appropriate care and love and attention to your kid can certainly reduce any potential harm.” Hurd says that one strategy to reduce harm is to be alert to signs of anxiety or hyperactivity in children and get them help right away”.
Other sources of anxiety in parents besides cannabis can also potentially be passed to children. Anxiety caused by worry associated to money, relationships, both busines and sexual, and other factors can have a genetic role in the anxiety levels inherited by children,
The researchers have based their finding on patterns found in the children of parents who smoked cannabis, absent in the children of none smoking mothers.
Other potential factors which could play an influential role is presumably taking into account by the analysis of placental tissues at the time of birth by the researchers.