Modelling model-based and model-free decision-making in a transdiagnostic sample to investigate disorder-specific and transdiagnostic alterations

Alterations in decision-making have been suggested to underlie different psychiatric illnesses, such as major depressive disorder (MDD), obsessive-compulsive disorder (OCD), and schizophrenia. Studies report overlapping and divergent alterations in individuals diagnosed with these disorders, which have been linked to symptoms of the respective disorders. One symptom characterizing all these disorders is impaired decision-making. To facilitate early diagnosis and treatment among these disorders which may also show comorbidities among each other, it is crucial to disentangle alterations in decision-making that are unique to specific disorders, from those that occur across diagnostic boundaries. Recent developments in computational modelling have enabled a mechanistic deconstruction of decision-making processes, facilitating the identification of disorder specific and disorder general alterations. We, therefore, employed two computational modelling approaches on to a two-step Markov decision task in a transdiagnostic cohort combining individuals diagnosed with MDD (N=23), OCD (N=25), and schizophrenia (N=27) to identify disorder specific and disorder general decision-making alterations, and associations with symptoms. The results revealed overall reliance on model-free decision-making behavior across all participants. Additionally, schizophrenia patients showed the lowest learning rate in stage one and highest switching rate (lowest perseverance) compared to all other groups. All patient groups were more random in their response profiles than controls in stage two, with schizophrenia patients revealing highest levels of randomness, while OCD patients were additionally more random in stage one compared to controls and MDD patients. Importantly, the findings revealed a correlation between increased model-free behavior and elevated depressive symptoms, while more model-based choices were linked to lower levels of anhedonia across all patients. Consequently, this study shows noteworthy disorder general and disorder specific decision-making alterations in individuals diagnosed with MDD, OCD, and schizophrenia, suggesting that concurrent alterations and symptoms might potentially have common underlying behavioral mechanisms. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study did not receive any funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethics committee of the Technical University of Munich gave ethical approval for this work. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The data for this study is available upon reasonable request to the corresponding author.