Adolescents can have post-traumatic stress reactions even when not directly affected by terrorist attacks such as the tragedy of 22 July 2011 in Norway. They are at increased risk if they have experienced violence or sexual abuse in early life.

Scientists have known little about reactions in young people who were neither directly affected nor had a close relationship with any of the victims.

Now a new study headed by researchers from Uni Research in Bergen, Norway, shows that the terror attacks of 22 July 2011 also affected the health of high school students who neither had physical nor psychological closeness to the attacks which cost the lives of 77 people.

Young people who have been victims of violence or sexual abuse as children, or who have witnessed violence, are more vulnerable to developing symptoms of post-traumatic stress - even if they only followed the media coverage of the terrorist attacks.

Those who have experienced sexual abuse numerous times have a doubled risk of post-traumatic stress reactions to a terrorist incident.

For those who have witnessed or been victims of violence the risk is 50 percent greater.

"Everyone involved in the health care of young people must be aware that those with negative past experiences may have a tough period even if they were not directly affected by the attacks."

Those are the words of researcher Dag Øystein Nordanger at Uni Research.

The researchers show that trauma in early life is an independent risk factor, representing vulnerability to respond to later traumatic events such as a terrorist act.

"If you see and read the media coverage, that can make you anxious and give you symptoms of post-traumatic stress," Nordanger added.

The study has analysed data from the research project ung@hordaland, a unique comprehensive survey of mental health and everyday functioning in more than 10 000 high school students over time.

"Our findings are important because they tell us that prevention of violence and abuse early in life also means preventing negative reactions to major incidents that occur later," said Nordanger.

He also pointed out that there is now a greater focus on the prevention of violence and traumatic stresses in childhood.

Nordanger said that researchers are now beginning to understand more of the consequences of earlier traumatic events.