Both positive and negative experiences influence how genetic variants affect the brain and thereby behavior, reveals a new study.
Sheilagh Hodgins of the University of Montreal said the evidence 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.
The researchers conducted a study to determine whether juvenile offending was associated with interactions between three common genetic variants and positive and negative experiences.
The Monoamine oxidase A (MAOA) gene is a key enzyme in the catabolism of brain neurotransmitters, monoamines, especially serotonin. Catabolism is the breaking down of complex materials and the releasing of energy within an organism.
Hodgins said that about 25 percent of Caucasian men carry the less active variant of MAOA and among them , those who experience physical abuse in childhood are more likely than those who are not abused to display serious antisocial behaviour from childhood through adulthood, while among females it is the high activity variant of the MAOA gene that interacts with adversity in childhood to increase the likelihood of antisocial behaviour.
The researchers 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.
They said that 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. Thus, the same genetic variants were associated with high and low levels of delinquency depending on exposure to negative or positive environments.
The study was published in the International Journal of Neuropsychopharmacology.