Shyness may be genetically inherited, according to new research from the Universite de Montreal in Canada. Antisocial behavior could also be triggered by genes, the study reveals.
Three genes seem to control the tendencies, with behavior developing based on the environment in which they are raised. Geneticists often say that genes load the gun of genetic problems, while environment pulls the trigger. Common variants of these three genes can bring about shyness in children raised in caring households, while youth raised in abusive homes often become antisocial.
"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. 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," Sheilagh Hodgins of the University of Montreal said.
A total of 1,337 high school students from Sweden participated in the study, answering questions about family history, including reporting on domestic violence, sexual abuse, delinquency, and the nature of their relationships with parents. All subjects in the study were aged between 17 and 18.
The students also provided saliva samples for researchers, from which DNA was extracted and examined. The Monoamine oxidase A (MAOA) gene helps to generate energy from molecules, for use by neurotransmitters in brains. Researchers found that less-active variations of the genes often led to antisocial behavior in males. Roughly 25 percent of males exhibit the variant. In females, problems tend to crop up in those with over-active MAOA genes.
A second gene, neurotrophic factor (BDNF), was also found to partially direct tendencies toward antisocial activities. This section of genetic code normally directs neuronal plasticity, changes in brains caused by injury or environmental damage.
"The low expressing variants of BDNF are carried by approximately 30% of individuals and some previous studies had shown that this variant was associated with aggressive behaviour if carriers were exposed to aggressive peers," Hodgins told the press.
The third gene is a serotonin transporter called 5-HTTLPR, which can lead to antisocial behavior in those people with low-activity variants of the sequence.
Together, the three genes act to predispose people toward antisocial behavior, with the form varying, depending on living conditions in their homes.
"These findings add to those from other studies to show that genes affect the brain, and thereby behaviour, by altering sensitivity to the environment," Hodgins stated in a press release.
