Children prenatally exposed to opioids alone have an increased risk of attention-deficit/hyperactivity disorder (ADHD), but interactions between opioids and both cannabis use and alcohol use were linked to varying levels of ADHD risk as well, according to findings published March 11 in JAMA Network Open.
While many prenatal exposure studies examine associations with one substance, the results of this case-control study “suggest that it is important to consider prenatal exposure to multiple substances and the interactions between these substances when counseling women regarding substance use during pregnancy,” wrote Henri M. Garrison-Desany of the Johns Hopkins University, Baltimore, and colleagues.
Using data from children in the prospective Boston Birth Cohort between 1998 and 2019, the researchers did a secondary analysis on the 3,138 children (50.4% of whom were male) with at least 2 years of follow-up, excluding children from multiple-gestation pregnancies, in vitro fertilization pregnancies, and deliveries involving major maternal trauma or major chromosomal anomalies. Mothers answered a questionnaire within 24-72 hours of delivery regarding their demographics, substance use, pregnancy history, and health status. Among the mothers, 58.6% were Black, 22.3% were Hispanic, 7.2% were White, 1.5% were Asian, and 10.4% were other races/ethnicities.
The children’s electronic medical records were used to identify those with ADHD diagnoses. The researchers did not assess prescription opioid exposure during pregnancy, but they based opioid exposure on mothers’ reports of recreationally using heroin or oxycodone, mothers’ reports of receiving methadone treatment, or a newborn diagnosis of neonatal abstinence syndrome or neonatal opioid withdrawal syndrome.
Just under a quarter of the women (24.2%) reported using at least one substance during pregnancy. After tobacco smoking (18.5%), the next most reported substances were alcohol (8.1%), cannabis (3.9%), and opioids (1.9%). With a median 12 years of follow-up, 15.5% of the children had been diagnosed with ADHD, most of whom (71.6%) were male.
Before considering interaction of different substances, children exposed to opioids had a little over twice the risk of ADHD (hazard ratio [HR], 2.19) compared to those with no prenatal substance exposure. Although neither cannabis nor alcohol was independently associated with ADHD, smoking had a 40% increased risk, and researchers found a 21% increase in risk of ADHD with each additional substance mothers used during pregnancy. The researchers had adjusted these findings for maternal age, race/ethnicity, marital status, educational level, annual household income, parity, number of perinatal visits, and general stress during pregnancy, based on a structured interview.
When the researchers considered all the substances together, opioid exposure increased risk of ADHD by 60% (HR, 1.6), opioids with cannabis increased risk by 42%, opioids with alcohol increased risk by 15%, and opioids with smoking increased risk by 17%.
”Our findings suggest opioids may interact with other substances (including cannabis), which may be particularly deleterious,” the researchers reported. “It is not clear whether this interaction is owing to biological or environmental factors, such as whether individuals with illicit polysubstance use are more likely to use more substances or whether they have other characteristics that may impact child development.”
The authors noted that cannabis exposure has been linked to other neurodevelopmental outcomes, including reduced executive and motor function in infants. ”Notably, although we did not find a significant independent association between cannabis exposure and ADHD, children exposed to both cannabis and opioids had a 23% greater risk than expected from either exposure individually,” they reported.
The researchers suggest that their findings provide data for considering harm reduction approaches that reduce use of any single substance during pregnancy. “Focusing on the most obviously harmful exposures may be a useful way to reduce the risk of ADHD,” they wrote. “Further work is needed to directly investigate this hypothesis and examine whether reduction in the use of any substance among those with polysubstance use could be acceptable compared with abstinence.”
In an invited commentary, Angela Lupattelli, PhD, and Nhung T. H. Trinh, PhD, both of the department of pharmacy at the University of Oslo, noted the methodological challenges of assessing exposures and associations from multiple different substances during pregnancy.
“First, how can we disentangle the consequences of individual and/or combined substance exposures during pregnancy from the underlying risks?” they asked. In addition to differences in baseline characteristic between those who use opioids or cannabis, Dr. Lupattelli and Dr. Trinh noted that other important unmeasured factors, such as genetics and family environment, may confound the effect size estimates for ADHD.
They also noted the need to consider intensity, dose, duration, and timing of substance use during pregnancy.
“Understanding the longer-term safety of substance use during pregnancy is paramount to inform prevention policy and shape counseling strategies. Observational studies, despite their limitations, are a necessary piece of the puzzle,” they wrote. “However, the study findings should be interpreted with caution, as the use of advanced analytical methods cannot overcome the unavailability of some important confounding factors and exposure information.”
The research was funded by the U.S. Department of Health and Human Services and the National Institutes of Health. The authors had no industry-related disclosures.