Effects of Traumatic Experiences on Information Processing in Patients with Mental Health Problems Abstract All human experiences have an effect on the brain, and in the form of memories and cognitive biases, affect the response of the individual to future events. When people experience traumatic events the brain is sometimes impacted in extreme ways, with major consequences for the individual in the form of psychiatric illness. This study is concerned with examining the way in which the prior experience of traumatic events affects the processing of simple stimuli under experimental conditions, in order to understand better the types of cognitive biases involved in psychiatric illnesses. The study used a well-established computerized test of selective attention, inhibition of return (IOR), and a newer task involving facial expressions and gaze cues. A review of the use of the IOR paradigm in different adult psychiatric disorders was conducted in order to aid interpretation of the findings. The mental health status of the participants was described by use of a number of standardized questionnaires. Participants were people in contact with Adult Mental Health services who had experienced trauma, including those with Posttraumatic Stress Disorder (PTSD), Psychosis and other psychiatric diagnoses. Results were compared with a healthy control group. Despite small sample sizes and heterogeneity within the groups, the study indicated that significant trauma can be associated with different types of mental health problem, and that different mental health problems are associated with different types of cognitive processing difficulty. The Psychosis group showed a lack of inhibitory processing, which is likely to be associated with increased distractibility, and, for example, lack of the ability to follow a train of thought. This is different from the distractibility seen in PTSD, which can be characterized as a tendency for attention to be captured by a salient stimulus without appropriate subsequent disengagement.