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The relationships among MAOA, COMT Val158Met, and 5-HTTLPR polymorphisms, newborn stress reactivity, and infant
Zdenka Bajgarova1, Adam Bajgar2
1Department of Pedagogy and Psychology, Faculty of Education, University of South Bohemia, Ceske Budejovice, Czech Republic.
Insights
Infant temperament is linked to how quickly cortisol levels decrease after stress. Specific gene variations influence both stress response and temperament traits in babies.
Area of Science:
- Neuroscience
- Genetics
- Developmental Psychology
Background:
- Infant temperament differences are linked to hypothalamic-pituitary-adrenal (HPA) axis reactivity.
- Cortisol interacts with dopamine and serotonin, suggesting gene polymorphisms affecting monoamine metabolism influence HPA axis reactivity and temperament.
Purpose of the Study:
- To investigate the relationship between specific gene polymorphisms (5-HTTLPR, MAOA, COMT), infant stress response (salivary cortisol), and temperament at 3 months.
- To understand how genetic variations in monoamine metabolism impact early HPA axis function and behavioral development.
Main Methods:
- Assessed salivary cortisol levels at three time points in 84 infants following a heel-stick blood draw.
- Measured infant temperament using Rothbart's Infant Behavior Questionnaire-Revised (IBQ-R) at 3 months of age.
- Analyzed associations between 5-HTTLPR S/L, MAOA H/L, and COMT Val158Met polymorphisms, cortisol response, and IBQ-R temperament scores.
Main Results:
- A greater decrease in salivary cortisol correlated with lower negative emotions, higher extraversion, and better regulation in infants.
- 5-HTTLPR S allele linked to higher negative emotionality and lower orienting/regulatory capacity.
- MAOA L allele associated with higher negative emotionality, lower regulatory capacity, and reduced cortisol decrease.
- COMT Val158Met Met allele linked to higher positive affectivity/surgency, better regulation, and greater cortisol decrease.
Conclusions:
- Cortisol elimination, not just basal levels or increase, is crucial for infant temperament.
- MAOA LL homozygotes showed higher cortisol increase, distress, negative emotionality, and approach, suggesting vulnerability to early stress and externalizing behaviors.
Introduction:
Variance in hypothalamic-pituitary-adrenal (HPA) axis reactivity is considered to be one of the sources of differences in infant temperament. The cortisol enters into interactions with dopamine and serotonin, so it is expected that polymorphisms in genes coding monoamine metabolism influence both HPA axis reactivity and temperament.
Methods:
We therefore explore the relationship among 5-HTTLPR S/L, MAOA H/L, and COMT Val158Met polymorphisms, the stress reaction of newborn infants after a heel stick blood draw (measured by determining salivary cortisol at three time points), and temperament assessed at the age of 3 months using Rothbart's Infant Behavior Questionnaire-Revised (IBQ-R) with a sample of 84 infants.
Results:
The decrease in the salivary cortisol correlated with nine primary scales and all three secondary scales of IBQ-R. Children with a greater cortisol decrease were assessed as less susceptible to negative emotions, more extraverted, and more regulated. The polymorphisms that were observed were related both to the course of the stress reaction and to temperament. The 5-HTTLPR S allele was connected to higher scores for Negative Emotionality and lower scores for Orienting/Regulatory Capacity. The presence of the MAOA L allele predisposed its carriers to higher scores for Negative Emotionality, lower scores for Orienting/Regulatory Capacity, and a lower decrease in cortisol. The Met allele of COMT Val158Met polymorphism was connected to a higher Positive Affectivity/Surgency and Orienting/Regulatory Capacity and a greater cortisol decrease.
Conclusions:
Contrary to previous studies referring mainly basal cortisol and its increase, the results of our study emphasize the importance of cortisol elimination in infant temperament. Another interesting finding was a higher cortisol increase, higher Distress to Limitations, Negative Emotionality, and Approach in MAOA LL homozygotes which are traditionally understood as more vulnerable toward early stress in developing later externalizing behavior.
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