IQ and non-clinical psychotic symptoms in 12-year-olds: results from the ALSPAC birth cohort - Horwood, Jeremy; Salvi, Giovanni; Thomas, Kate; Duffy, Larisa; Gunnell, David; Hollis, Chris; Lewis, Glyn; Thompson, Andrew; Menezes, Paulo; Wolke, Dieter; Zammit, Stanley; Harrison, Glynn (The British journal of psychiatry, 2008)