Although it is still a controversial topic some research has shown that using cannabis in adolescence is associated with an increased risk of developing psychosis. At the same time suffering childhood trauma is associated both with an increased risk of substance misuse and of developing psychosis. A team of Irish researchers tried to get to the bottom of the links between childhood trauma, substance abuse and psychosis in a study of 211 children aged between 12 and 15. They were asked about childhood trauma, cannabis use and any mental-health problems they might be having. The researchers found that both childhood trauma and cannabis use were significantly associated with an increased risk of developing psychosis symptoms. However, the presence of both childhood trauma and early cannabis use significantly increased the risk for psychotic symptoms beyond the risk posed by either factor alone.
Harley, M. ... [et al] - Cannabis use and childhood trauma interact additively to increase the risk of psychotic symptoms in adolescence Psychological Medicine, October 2010, 40(10), 1627-1634