Symptom-related attributional biases in schizophrenia and bipolar disorder

Introduction: Biases in causal attributions and evidence integration have been implicated in delusions, but have not been investigated simultaneously to examine additive or multiplicative effects. It was hypothesised that paranoid delusions would correlate with self-serving and personalising biases (defence model of paranoia), particularly when these biases were disconfirmed.Methods: Constrained principal component analysis was used to investigate differences between schizophrenia patients (paranoid vs. non-paranoid), bipolar disorder patients, and healthy controls, as well as to examine the extent to which psychotic symptoms could predict patterns of responding on a novel attributional bias task (Attributional Style BADE, or ASB) that requires integrating contextual information.Results: Although no group differences were found, disorganisation and manic symptoms correlated with situation attributions and self-blame when such attributions were unsupported by the available evidence, and depression and anxiety correlated with other-person and self attributions (not situation attributions) when confirmed by the available evidence, regardless of diagnosis.Conclusions: While group differences accounted for little variance in responses on the ASB task, a transdiagnostic association between symptoms of psychosis and the ASB task was observed. This highlights the importance of considering symptom profiles rather than diagnostic groupings when investigating cognitive biases and related non-pharmacological treatments.