Emerging research suggests that deficits in executive functioning are a core feature of mental disorders across the full spectrum of psychopathology. Cognitive training exercises that focus on improving executive functioning have been shown to reduce symptoms related to schizophrenia, major depression and ADHD, as well as eliciting changes in alcohol consumption. However, it is not yet clear whether such training is also effective in preventing the onset of psychological symptoms and substance use in adolescents at risk for developing a broad range of psychopathology. In a sample of adolescents (n=220), the current study will examine whether cognitive training is effective in reducing a range of psychopathology in youth at high risk for developing a mental illness, as determined by a standardised measure of personality. It is expected that a targeted cognitive training program will prevent the onset of a range of mental illnesses and substance misuse in high risk youth.