Gene that causes aggression in men under stress discovered

By Dr. Ananya Mandal, MDMar 11 2012

Scientists have found that “macho” gene that makes men behave more aggressively than women under stress. They say this one gene could explain why men have a 'fight or flight' response while women are more likely to try and defuse the situation. The study has been published in the journal BioEssays.

Scientists from Prince Henry's Institute for Medical Research in Melbourne have studied the chemicals secreted by men when they react to stress - and how this influences their behavior. They found that the SRY gene - only found on the Y chromosome - and the proteins it activates in the body are the key. This gene was previously thought just to be involved in the development of male characteristics in the womb.

But Joohyung Lee and Vincent Harley from Prince Henry’s Institute in Melbourne have shown these proteins are actually present in the brain and other organs of adult males. “Historically males and females have been under different selection pressures which are reflected by biochemical and behavioural differences between the sexes,” said Dr Joohyung Lee. “The aggressive fight-or-flight reaction is more dominant in men, while women predominantly adopt a less aggressive tend-and-befriend response.”

These genes may regulate stress hormones and blood pressure which cause stressed-out men to experience their pulse quickening and adrenaline coursing through their veins - triggering aggression.

Dr Lee and his institute study co-author Professor Vincent Harley say the SRY gene reveals a genetic underpinning for this difference, because of its role in controlling a group of neurotransmitters known as catecholamines. “Besides the testes, SRY protein is present in a number of vital organs in the male body including the heart, lungs and brain, indicating it has a role beyond early sex determination,” Prof Harley said. “This suggests SRY exerts male-specific effects in tissues outside the testes, such as regulating cardiovascular function and neural activity, both of which play a vital role in our response to stress.”

The scientists theorize the SRY gene may actually prime the organs of the male body to deal with stress, through an increased release of catecholamine and blood flow to organs. “New evidence indicates that the SRY gene exerts `maleness' by acting directly on the brain and peripheral tissues to regulate movement and blood pressure males,” Dr Lee said in a statement.

The scientists say women often respond differently because of estrogen and the activation of internal opiates, which may prevent aggressive responses. “This research helps uncover the genetic basis to explain what predisposes men and women to certain behavioral phenotypes and neuropsychiatric disorders,” he said. It could also explain why some conditions – such as Attention Deficit Hyperactivity Disorder, autism and Parkinson’s disease – affect more men than women.