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Health experts say there are a number of reasons why women should avoid cannabis during pregnancy. Mick Follari/Stocksy
  • A new study has found that children exposed to cannabis while in the womb are more likely to continue displaying symptoms of mental health issues as they age.
  • These symptoms can persist during adolescence, a critical time for brain development.
  • Previous studies have indicated cannabis use during pregnancy may lead to a higher risk of autism, behavioral issues, and lower intelligence in the child.

Experts recommend that recreational drugs be avoided during pregnancy as they may harm the baby’s development — and new research is now highlighting the potential lasting impacts of one concern in particular.

To explore the effects of cannabis intake during pregnancy on a child’s cognition, researchers at the Washington University BRAIN Lab in St. Louis compared data from almost 12,000 children, collected as part of the National Institute of Health’s ABCD study.

An initial exploration, conducted by the BRAIN Lab in 2020, looked at children (then aged 9-10) who were exposed to cannabis in the womb. Researchers said they found the children of mothers who continued to smoke cannabis once they learned they were pregnant were more likely to present with symptoms of mental health issues, which can contribute to conditions such as anxiety and depression.

Two years later, the team’s follow-up study looked at the same children (now aged 11-12) and saw that these symptoms continued to persist as they edged toward their teenage years.

The results came as a surprise to the researchers.

“My personal hypothesis was that they [the differences in symptoms between cannabis-exposed and non-exposed children] were going to shrink,” David Baranger, Ph.D., a neuroscientist and post-doctoral research associate at the BRAIN Lab and co-author of the study, told Healthline.

However, these differences “remained elevated, even as the kids grew older,” he noted.

Little research has been conducted into this area previously — so experts say these results are critical in increasing awareness.

The fact that symptoms continue to present as children move into adolescence is also significant, stated Baranger, as this is a crucial time for the brain.

“Adolescence is a period of fairly rapid brain development and maturation,” he said. “It’s a really critical period in a person’s life, and the brain continues to be shaped by its experiences.”

Baranger added that adolescence is also when mental health diagnoses are more likely to occur — and the existing vulnerabilities of children’s brains put them at greater risk of an official diagnosis.

Scientists are still exploring how cannabis affects a fetus’ brain development.

However, in the 2020 study, researchers proposed that endocannabinoid type 1 receptors — critical in fetal brain development — are negatively impacted by THC (the primary psychoactive component of cannabis).

These receptors do not develop in the fetus until around weeks 5 and 6 of pregnancy. Researchers said the children of those who smoked cannabis after this time were more likely to present with cognitive issues, while adverse cognitive effects were not seen in the children of mothers who stopped smoking cannabis at 6 weeks.

“Weeks 5-6 are a critical stage of development,” Dr. Whitney Booker, an OBGYN in the department of obstetrics and gynecology at Columbia University Medical Center in New York, explained to Healthline.

“The neural tube closes around week 4 and is the early derivative of the brain and spinal cord,” she continued.

Between weeks 5 and 8, the central nervous system starts to develop its vesicles, Booker added, “which are embryologic precursors to different structures of the brain.”

Additional studies have highlighted other cognitive outcomes that may arise when cannabis is consumed during pregnancy.

For instance, Booker highlighted a 2020 study that found that children exposed to cannabis in the womb were more likely to develop autism.

A 2008 study noted that cannabis-exposed children had lower levels of intelligence and memory, while some researchers in 2011 said they saw attention and behavioral concerns arising in infants as young as 18 months of age.

It’s not only brain development that can be affected by cannabis consumption during pregnancy.

“Multiple studies have shown cannabis use may be associated with increased risk of small-for-gestational-age infants and low birth weight,” Dr. Juan Sanchez, an OBGYN at the Sunset Park Family Health Center at NYU Langone in New York, told Healthline.

And, he added, “those who use cannabis at higher doses seem to have an even higher risk [of these].”

Furthermore, Sanchez explained, smoking cannabis may impair blood supply to the placenta, “which can cause complications with the developing fetus.”

Indeed, it’s been suggested that cannabis consumption may hinder nutrient and oxygen availability to the developing fetus.

As such, organizations such as the American College of Obstetricians and Gynecologists, the Centers for Disease Control and Prevention, and the Food and Drug Administration recommend against using any cannabis products while pregnant.

In the 2022 follow-up study, researchers noted that children exposed to cannabis in the womb were more likely to exhibit symptoms of anxiety and depression.

So what do these entail?

“Anxiety is the most common mental health issue in childhood,” Catherine Hallissey, a child psychologist in Ireland, told Healthline.

She noted that younger children often experience separation anxiety, while “older children and teenage anxiety tends to be focused on school or social anxiety.”

Hallissey said that signs of anxiety include:

  • Frequent thoughts of worry
  • Focusing on the negative
  • Changes in eating habits
  • Difficulty falling asleep or experiencing nightmares
  • Tummy aches and frequent toilet trips
  • Trouble concentrating
  • Increased crying, angry outbursts, and irritability

What about depression?

“Clinical depression is extremely uncommon in childhood and early adolescence,” Hallissey stated. Instead, periods of low moods are more likely to be seen.

Low moods can last for days or weeks, she explained, and present as:

  • Periods of sadness
  • Worry
  • Frustration or anger
  • Low self-esteem
  • Tiredness
  • Anxiety

However, if symptoms persist, “it may be a sign of depression,” she said. In this case, other signs include:

  • Not showing interest in things they previously enjoyed
  • Changes in sleeping or eating habits
  • Feeling hopeless
  • Difficulty concentrating
  • Thoughts of self-harm or suicide

Showing your child that you’re there to support and listen can be helpful, but “it’s a good idea to get professional help if things are not improving after a few weeks, especially if it’s impacting family life, friendships or school,” Hallissey said.

The number of women in the United States using cannabis during pregnancy continues to rise, with many utilizing it to ease pregnancy-related symptoms.

Yet, despite this increase and initial studies emphasizing its potential influence, research on cannabis and fetal development remains relatively low.

As such, experts say these new findings are important in reiterating the potentially detrimental effects of cannabis intake on fetal brain development.

Looking ahead, the BRAIN Lab researchers will continue to track the same children in the ABCD dataset to monitor for changes in cognitive outcomes.

They are also undertaking a new study, tracking cannabis-using mothers and their children from the early stages of pregnancy — instead of launching their analysis in later life.

“We hope that, by following this cohort during the pregnancy, we’ll get a better insight,” stated Baranger.