Tags: Cannabis; autism; pregnancy;

 

Thumbnail:  This report retrospectively analyzes birth data and maternal cannabis use to investigate associations between cannabis use and the neurodevelopmental outcomes of the child. They found an association between maternal cannabis use during pregnancy and an increased incidence of Autism Spectrum Disorder (ASD) or other intellectual/learning disorders in the child. However, the authors caution that this association may also be influenced by unknown factors that were not assessed.

 

The problem: As the legal status of cannabis changes, it is becoming more widely available and more frequently used. This includes more frequent use by women throughout their pregnancy. Cannabinoids (the active compounds in cannabis), such as THC, cross the placenta during pregnancy, and previous research has suggested that exposure to these compounds in utero may disrupt the developing fetal neural network. Therefore, there is concern about the potential impact this may have on the childhood development of the offspring.  

 

The study: This study reviewed data from all live births in Ontario, Canada across a span of 5 years using the BORN Ontario birth registry. 508,025 children were included in the final analysis and data from the provincial health administrative database was used to assess their childhood development. Factors included in the assessment of neurodevelopmental outcomes were diagnoses of ASD, intellectual and learning disorders, and attention deficit hyperactivity disorder (ADHD).

 

Main Points:

• The incidence of ASD among children exposed to cannabis in utero was 1.5 times higher than that of children who had no exposure.

• Comparing the incidence of ASD across income levels found that income had no effect.

• Rates of intellectual and learning disorders were slightly higher (1.2x) among children with prenatal cannabis exposure, however the difference was not significant.

• The incidence of ADHD was slightly higher (1.1x) among children exposed to cannabis during pregnancy, but this difference was not significant.

 

Conclusions: Prenatal exposure to cannabis appears to result in a higher risk of ASD. However, these results should be interpreted cautiously, as there may be additional, unidentified, factors playing a role here.

 

Why this is a good study:

• This study looks at a very large number of people, which minimizes potential biases and makes the results more robust

• The authors use multiple statistical analyses to validate and confirm the risk assessments reported here

 

Why this isn’t a perfect study:

• The prevalence of cannabis use reported in this study was lower than reported elsewhere, which may mean that some cannabis users were misclassified as non-users in the database, which would effect the analysis

• Data on cannabis use in this registry is self-reported, so not all users may have reported their cannabis use

• The frequency, duration and timing (what trimester) of cannabis use was not available, which may have been helpful in analyzing the risks resulting from cannabis use

• This is an observational study which can be more easily impacted by confounding factors, like a misdiagnosis

 

What this study adds:

• There are not many longitudinal studies looking at the effects of cannabis over time. This study is among the first to follow children and look at the effects of maternal cannabis use on the neurodevelopment of children.

 

What it doesn’t:

• This study does not conclusively prove that cannabis is solely responsible for the association reported here.

• This study is unable to shed any light on how different patterns (frequency, duration, timing/trimester) of cannabis use may effect neuronal development

 

Funder: None stated

 

Author conflicts: None declared