Overall, 15.1 per cent of participants reported lifetime use, 10.3 per cent reported past year use, and 7.2 per cent reported use in the past month of any substance, the study found.

Three other service members were injured in the attack, during which the gunman was “engaged and killed”, according to the US military. 

​Three other service members were injured in the attack, during which the gunman was “engaged and killed”, according to the US military.  

In central Syria an ISIS gunman ambushed US forces near Palmyra, claiming the lives of two American service members and one civilian. Three other troops sustained injuries in the attack. The gunman was neutralized by forces. This incident marks the first US casualties in Syria since a significant political shift a year ago.