J Psychiatry Neurosci 2015;40(6):422-428
Christina Andreou, MD, PhD; Brooke C. Schneider, PhD; Vivien Braun, MD, PhD; Katharina Kolbeck, MD, PhD; Jürgen Gallinat, MD, PhD; Steffen Moritz, PhD
Background: Disturbances in evidence gathering and disconfirmatory evidence integration have been associated with the presence of or propensity for delusions. Previous evidence suggests that these 2 types of reasoning bias might be differentially affected by antipsychotic medication. We aimed to investigate the effects of a dopaminergic agonist (L-dopa) and a dopaminergic antagonist (haloperidol) on evidence gathering and disconfirmatory evidence integration after single-dose administration in healthy individuals.
Methods: The study used a randomized, double-blind, placebo-controlled, 3-way crossover design. Participants were healthy individuals aged 18–40 years. We administered a new data-gathering task designed to increase sensitivity to change compared with traditional tasks. The Bias Against Disconfirmatory Evidence (BADE) task was used as a measure of disconfirmatory evidence integration.
Results: We included 30 individuals in our study. In the data-gathering task, dopaminergic modulation had no significant effect on the amount of evidence gathered before reaching a decision. In contrast, the ability of participants to integrate disconfirmatory evidence showed a significant linear dopaminergic modulation pattern (highest with haloperidol, intermediate with placebo, lowest with L-dopa), with the difference between haloperidol and L-dopa marginally reaching significance.
Limitations: Although the doses used for haloperidol and L-dopa were similar to those used in previous studies, drug plasma level measurements would have added to the validity of findings.
Conclusion: Evidence gathering and disconfirmatory evidence integration might be differentially influenced by dopaminergic agents. Our findings are in support of a dual-disturbance account of delusions and provide a plausible neurobiological basis for the use of interventions targeted at improving reasoning biases as an adjunctive treatment in patients with psychotic disorders.
Submitted Oct. 17, 2014; Revised Jan. 16, 2015; Accepted Feb. 27, 2015; Early-released July 21, 2015.
Acknowledgments: This word was supported by a grant to C. Andreou by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG, Project-Nr: AN970/1-1). The authors thank Yanis Konstantinou and Mihail Mihov for programming the Box Task.
Affiliations: From the Department of Psychiatry and Psychotherapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Competing interests: J. Gallinat reports receiving speaker fees from Janssen and a grant from Astra outside the submitted work. No other competing interests declared.
Contributors: C. Andreou, J. Gallinat and S. Moritz designed the study. V. Braun and K. Kolbeck acquired the data, which C. Andreou, B. Schneider, J. Gallinat and S. Moritz analyzed. C. Andreou wrote the article, which all authors reviewed and approved for publication.
Correspondence to: C. Andreou, University Medical Center Hamburg-Eppendorf, Department of Psychiatry and Psychotherapy, Martinistrasse 52, 20246 Hamburg, Germany; email@example.com