Early inhibitory control and working memory abilities of children prenatally exposed to methadone

Methadone maintenance is the most common method of treating opioid-dependent pregnant women. However, little is known about the impact of prenatal methadone exposure on child neurocognitive development.

To examine the early executive functioning of children born to methadone-maintained mothers, and to assess relations between executive functioning and later emotional and behavioral adjustment.

Prospective longitudinal study.

The sample consisted of 68 methadone-exposed children and 88 non-methadone-exposed children.

At age 2years, children's inhibitory control and working memory were assessed using the Snack Delay and Three Boxes tasks. At 2 and 4.5years, their emotional and behavioral adjustment was assessed using the caregiver-completed Strengths and Difficulties Questionnaire.

Methadone-exposed children had poorer inhibitory control than non-exposed children (p<0.0001). These differences were explained by maternal education and prenatal benzodiazepine use. With respect to working memory, although both groups performed similarly on the first trial set, non-exposed children significantly improved their performance on the second trial set (p=0.002), while methadone-exposed children did not (p=0.92). Inhibitory control at age 2years was predictive of higher conduct (p=0.001), hyperactivity (p=0.0001), peer relationship (p=0.02), and total (p<0.0001) problems at 4.5years even after adjustment for behavioral problems at 2years.

Methadone-exposed children demonstrate difficulties with inhibitory control and possibly sustained attention/learning. These difficulties were explained by factors correlated with maternal prenatal methadone use. Longer-term follow-up of these children is needed to understand the effects of prenatal methadone exposure and related maternal factors on executive functioning and behavioral adjustment.