[1] Cardiff Univ, Wales Coll Med, Dept Med Psychol, Cardiff CF4 4XN, Wales
[2] Cardiff Univ, Wales Coll Med, Biostat & Bioinformat Unit, Cardiff CF4 4XN, Wales
[3] Univ Birmingham, Queen Elizabeth Psychiat Hosp, Div Neurosci, Birmingham B15 2TH, W Midlands, England
[4] Newcastle Univ, Dept Psychiat, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England