A study of Swedish teenagers revealed how three genetic factors work together to influence antisocial behavior.
The study found both positive and negative experiences have an effect on the brain and behavior, the University of Montreal reported.
"Evidence is accumulating to show that the effects of variants of many genes that are common in the population depend on environmental factors. Further, these genetic variants affect each other," said Sheilagh Hodgins of the University of Montreal and its affiliated Institut Universitaire en Santé Mentale de Montréal. "We conducted a study to determine whether juvenile offending was associated with interactions between three common genetic variants and positive and negative experiences."
To make their findings, researchers looked at 1,337 teenagers who completed questionnaires on "delinquency, family conflict, experiences of sexual abuse, and the quality of their relationship with their parents." They also provided a sample of saliva in which DNA was extracted from.
The team found the Monoamine oxidase A (MAOA) gene played a role in which participants exhibited antisocial behavior.
"About 25 [percent] of Caucasian men carry the less active variant of MAOA. Among them, those who experience physical abuse in childhood are more likely than those who are not abused to display serious antisocial [behavior] from childhood through adulthood," Hodgins said. "Among females it is the high activity variant of the MAOA gene that interacts with adversity in childhood to increase the likelihood of antisocial [behavior]."
The brain-derived neurotrophic factor (BDNF) gene, which is involved in neural plasticity, was found to be linked to aggressive behavior. The third gene the researchers looked at, serotonin transporter 5-HTTLPR, made carriers more susceptible to antisocial and aggressive tendencies if exposed to adversity in childhood.
"We found that the three genetic variants interacted with each other and with family conflict and sexual abuse to increase the likelihood of delinquency, and with a positive parent-child relationship to decrease the risk of delinquency," Hodgins said. "Among carriers of the low activity variants of all three genes, those exposed to family conflict or sexual abuse or both reported high levels of delinquency while those who reported a positive and warm relationship with their parents reported little or no delinquency"
The findings back up past evidence that genes affect the brain and how it influences behavior.
The findings were published Dec. 11 in the International Journal of Neuropsychopharmacology.
