Certain brain regions light up when mothers view the smiling face of their own infant. But a new brain imaging study suggests that this natural response is muted among mothers with a history of substance addiction.

“Normally, when a mother sees her own baby, particularly her smiling baby, it produces an increase in brain response in reward areas, which is thought to elicit caregiving behavior,” study author Sohye Kim, an assistant professor at Baylor College of Medicine, explained to PsyPost.

“This was shown in Dr. Lane Strathearn’s (who is the senior author of the study) previous study and was featured in ABC’s Good Morning America several years ago,” she said.

“We wanted to understand what’s happening in a mother’s brain when she engages with her baby, when there are complicating drug addiction problems. Unlike many mothers who find engaging with their infants to be a uniquely rewarding and gratifying experience, mothers with addiction problems may be less able to respond appropriately to their babies.”

“This group is traditionally known to be at high risk for child abuse and neglect. Despite the reported difficulties, little is known about how drug addiction changes brain response related to maternal behavior. This is the first human study that examined how the mother’s brain response to her own infant is modified in the presence of drug addiction.”

The new study was published online July 26 in the scientific journal Human Brain Mapping.

“We used functional magnetic resonance imaging (fMRI) to examine brain activity in 36 mothers who used addictive substances during pregnancy,” Kim explained. “The brain scan allowed researchers to observe how the mother’s brain reward mechanisms responded when she looked at her baby’s face, compared to when she looked at the face of an unknown baby.”

The mothers were recruited from an inpatient treatment facility for substance use disorders. Women with severe psychiatric symptoms or a diagnosis of schizophrenia were excluded from the study.

“When addicted mothers saw their babies’ smiling faces, the reward regions in the brain were not activated,” Kim said. “The smiling cue is probably the most rewarding cue one can get from one’s own baby. However, even though they were seeing the most rewarding from their own baby, the key reward regions of the brain appear to be ‘shut down’ in these mothers.”

The researchers observed muted responses in the amygdala, hippocampus, thalamus, cingulate, ventral tegmental area and substantia nigra. These areas of the brain have been linked to social cognition and empathy.

“This is a powerful contrast to what we saw in previous studies done with non-addicted mothers, which showed a powerful reward response to their smiling baby — this is what you would expect from new mothers,” Kim said. “You want mothers to find it inherently rewarding to attend to and engage with their baby. You want them to be motivated and interested in caring for their own baby, despite feeling exhausted as a new mother.”

The research does have some caveats. Sixty-seven percent of the participants were taking medications at the time of the study, including antipsychotic medications and drugs for depression or anxiety.

“Our study showed that the brain reward system of these mothers appeared to be shut down when looking at their own infant’s smiling faces. We are now trying to understand what directly contributes to these findings,” Kim remarked. “Is it the use of addictive drugs themselves? Or, is it these mothers’ history of trauma from their own early life?”

“The majority of these mothers have a history of early trauma that remains unresolved to date. This is what we are trying to address in the next phase of our study.”

“In the next phase of the study, we are also trying to examine whether giving oxytocin through intranasal sprays, which is a simple, low-risk pharmacologic intervention, can enhance brain reward response in these mothers. Oxytocin is a hormone important in mother-infant attachment.”

The study, “Mothers with substance addictions show reduced reward responses when viewing their own infant’s face“, was also co-authored by Udita Iyengar, Linda C. Mayes, Marc N. Potenza, and Helena J. V. Rutherford.