Science

Cannabis exposure in pregnancy affects cognition in offspring

cannabis
Study shows cannabis exposure during pregnancy is linked to cognitive problems in offspring. Source: lovingimages (via Pixabay)
A new study Washington State University's Integrative Physiology and Neuroscience unit reveals cannabis exposure in pregnancy affects cognition of offspring.

By Alex Brown | Contributor

Cannabis, also known as ‘weed’ or ‘marijuanna’ is the most commonly used illicit drug in the UK. The substance obtained from the cannabis plant has the chemical tetrahydrocannabinol (THC), which when inhaled or ingested can have hallucinogenic effects and can alter a person’s state of mind and their mood.

Research conducted by neuroscientists at Washington State University could help unveil the effects smoking marijuana has on babies, helping Mothers’ to make more informed decisions during pregnancy. The team’s findings were published in the journal, Neuropharmacology. 

Halle Weimar, lead researcher said:

 ‘[At present] the reality of cannabis research is there is not a lot of it’ 

This may be alarming to some, as roughly 2 million people in Britain admit to smoking marijuana weekly, and with 59% calling for the legalisation of recreational cannabis in Britain, many top politicians believe the drug will be legalised in the next 5-10 years.

In the study conducted in Washington State University’s Integrative Physiology and Neuroscience unit  pregnant female rats were delivered cannabis vapour before and during their entire 3-week gestation period. The methodology aimed to replicate how humans use cannabis, more specifically how pregnant women may use the drug. Following this, they delivered propylene glycol vegetable glycerol mixture(a common component in vape juice), to explore its effects in the rats. A control group with no exposure to the vapor was also used. The vapor was administered twice daily to the rats for an hour during the mating period and pregnancy.

The researchers found significant behavioral changes and cognitive deficits that continued into adulthood in the offspring of the rats exposed to cannabis during their pregnancy. Using levers and light cues, rats were trained to press a specific lever with a light cue in order to receive a sugar pellet reward. Subjects were then challenged to change their strategy during test day and ignore the light cue, as a way of measuring cognitive flexibility.

The results showed that regular cannabis exposure on rats during pregnancy may cause their offspring to have long term cognitive deficiencies, asocial behavior, and anxiety. The offspring of pregnant rats exposed to cannabis vapor were more likely to make regressive errors after they had been taught a new method to receive sugar pellets. Weimar explained:

“While rats eventually caught on, those whose mothers were exposed to cannabis were more likely to revert to the old pattern and make regressive errors…They also took more trials to learn the rules.”

The rats were also more antisocial and less playful. Both male and female juveniles whose mothers were exposed to vapour engaged in fewer play behaviours, while male rats were particularly hesitant to engage with other rats in initial social introductions.

Additionally, adult rats exposed to cannabis gestationally exhibited anxiety-like behaviour in new environments. Both control and cannabis exposed rats were placed in a large, elevated maze with open and close arms. Rats exposed to cannabis were more likely to stay within the confines of the closed sections and were less likely to explore the open exposed arms. These findings were significant because they showed the offspring had age-dependent effects well into adulthood, as this behaviour was not displayed in juvenile rats.

Behavioural changes were also noted in young rats. Weimar found that rats with cannabis exposure during pregnancy made more than a hundred ultrasonic vocalizations, or cries for their mothers, than the control group rats. When reflecting on this, Weimer commented, 

“It’s pretty noteworthy because this is one of the only tests you do that looks at emotional reactivity in neonates and they were far more reactive than the other groups.”

These findings highlight the need for further research to assess how cannabis affects not only the user, but also how it passively affects those around them. This can enable people to make informed decisions before taking cannabis or supporting its legalisation.

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