Children of mothers who use cannabis are much more likely to die in the first year of life

A new analysis of hospital discharges in California showed that 1% of children whose mothers were diagnosed with the cannabis use disorder died in the first year of life. This percentage was 0.4% for mothers without this disorder. The study was published in Drug and Alcohol Dependence.

Cannabis use disorder is a problematic pattern of using cannabis that leads to clinically significant impairment or distress. It is defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) as a condition in which individuals continue to use cannabis despite experiencing negative consequences, such as problems with interpersonal relationships, work or school performance, or mental and physical health.

Tetrahydrocannabinol (or THC) is the main psychoactive chemical in cannabis. In pregnancy, it readily crosses the placenta and can accumulate in the fetus. It is thought that exposure to it before birth dysregulates the endocannabinoid system, one of the systems vital for the implantation of fetus into the placenta and its development.

The U.S. national surveys of Drug Use and Health from 2016-2017 showed that about 12% of pregnant women reported using cannabis in the past 30 days during their first trimester of pregnancy. This number dropped to 4% for the second and third trimester.

This happens in spite of studies showing that cannabis use during pregnancy is associated with a 61% higher risk of the baby being small, 106% higher risk of the infant having low weight at birth, 38% higher risk that the baby will require intensive medical care after birth, and a 28% increased risk that it will be born prematurely.

To further investigate the association between cannabis use disorder in pregnant women and death and sickness of infants, study author Gretchen Bandoli and her colleagues analyzed data from the Study of Mothers and Infants collected between 2011 and 2018. This study included administrative records of all births in California in the mentioned period.

The study authors linked these records with a number of health service records for the mother and the infant and with the California death files to capture deaths of infants and mothers that occurred in California during the first year after birth of the infant. The final study sample consisted of somewhat less than 3.5 million singleton births born between 20- and 44-weeks gestational age.

The researchers analyzed data on the presence of the diagnosis of cannabis use disorder in the health records of the mother, infant emergency department visits and re-hospitalizations after birth, and infant death in the first year of life (whether it had occurred or not, established from the California death records and hospital discharge summaries) with the cause of death if the infant died. They also collected data on race/ethnicity of the mother, her age, education, presence or absence of mental health conditions, and the source of payment for the hospital services.

Results showed that 1% of mothers had a diagnosis of cannabis use disorder. This percentage increased from 0.7% to 1.4% between 2011 and 2018. These mothers were less likely to be Hispanic or Asian and more likely to be White, American Indian/Alaska Native or Black compared to those without cannabis use disorder diagnosis. Mothers with this disorder were also more likely to be younger than 18, have public health insurance, and to have less than 12 years of education.

Infants of mothers with cannabis use disorder had somewhat higher incidences of hospital readmission and emergency department visits compared to infants whose mothers did not suffer from this disorder. When researchers controlled for a list of characteristics of mothers, this difference disappeared. Characteristics they controlled for were the body mass index before pregnancy, race/ethnicity, the source that paid medical services for the delivery of the baby, anxiety diagnosis, depression diagnosis, bipolar disorder, prenatal nicotine use, alcohol use diagnosis, other substance use diagnoses, and mother’s age.

1% of infants whose mothers had cannabis use disorder died during their first year of life compared to 0.4% of infants whose mother did not have this disorder. The increased risk of death was more than halved when researchers controlled for the characteristics of mothers (those mentioned above), but still remained 1.4 times higher than that of infants whose mothers did not suffer from cannabis use disorder.

“When examining specific causes of death, the increased risk estimates were attributable to perinatal conditions and sudden unexpected infant death,” the researchers wrote and added that 40% of the excess risk came from the premature birth of the infant.

Additionally, the study found that mothers diagnosed with cannabis use disorder were much more likely to die themselves during the first year of an infant’s life compared to mothers without this disorder. Without adjusting for personal characteristics of mothers, the risk of death was 5 times higher in this group, but only 1.2 times higher when adjusting for other variables.

These findings add to the growing literature on the adverse outcomes linked with the exposure of a developing fetus to cannabis. However, it also has limitations that need to be considered. Namely, authors note that there is likely a bias present on who receives the diagnosis of the cannabis use disorder, this diagnosis being more likely in individuals on public health insurance and who already have other substance use and mental health diagnoses.

“There are very likely individuals who use similar or greater amounts of cannabis who don’t receive a CUD [cannabis use disorder diagnosis], which could bias our estimates towards the null,” the researchers noted. Additionally, the study did not take into account environments in which infants lived.

The study, “Prenatal cannabis use disorder and infant hospitalization and death in the first year of life”, was authored by Gretchen Bandoli, Erin Delker, Benjamin T. Schumacher, Rebecca J. Baer, Ann E. Kelly, and Christina D. Chambers.

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