The European prevalence of psychotic disorders including schizophrenia is 1.2%; this corresponds to approximately 40, 164 patients in Ireland, with an estimated cost (direct and indirect healthcare costs) of approximately €1 BN per annum. Schizophrenia is associated with a breakdown of an attentional filter; this is reflected by allocation of salience to irrelevant information. Salience processing deficits in schizophrenia may lead to spurious associations being formed between various pieces of information in the environment, from which unusual thought patterns and symptoms (i.e., delusions) are formed. The inability to allocate attention appropriately in schizophrenia is linked with dysregulation of the neurotransmitter dopamine in the brain. Drugs of abuse, in particular cannabis, can also produce transient psychotic symptoms in healthy individuals and can worsen psychotic symptoms in people with schizophrenia; these drug-induced effects likely reflect disturbance in dopaminergic function. It is currently unknown whether a history of drug abuse is associated with increased severity of salience processing deficits in psychotic patients. This study aims to carry out this test within a population of psychotic patients and compare these findings to those of a control population, with no history of psychosis or psychiatric conditions. There are certain assessments which allow salience misattribution to be tested; two such measures are the Kamin blocking and “White Noise” tasks, which measure reward-related and emotional salience processing respectively. We will investigate the relationship between salience processing status, self-reported history of substance use, type and severity of symptoms in patients diagnosed with a psychotic disorder vs. healthy controls.
