Between fifteen and twenty per cent of people with learning disabilities have behaviour problems. Researchers from Vanderbilt University in Tennesee have been looking at how genetics might play a part in this. They looked at a gene linked to a substance called monoamine oxidize A (MAOA) which in turn regulates the neurotransmitters serotonin (linked to appetite and mood) and norepinephrine (linked to the 'fight-or-flight' response). Previous studies have linked a variation in this gene to violent behaviour. The researchers studied 105 men between the ages of 18 and 50. Some had learning disabilities and a history of violent behaviour, others had learning disabilities but no history of violent behaviour while the remainder formed a control group of men with no learning disabilities and no history of violence. The researchers found that 43% of those with learning disabilities and a violent past had the gene variation compared to only 20% of the other two groups.
You can find out more about this research at