ORIGINAL INVESTIGATION Probability discounting of treatment decisions in multiple sclerosis: associations with disease knowledge, neuropsychiatric status, and adherence Jared M. Bruce 1,2 & Amanda S. Bruce 3,4 & Sharon Lynch 5 & Joanie Thelen 1 & Seung-Lark Lim 1 & Julia Smith 1 & Delwyn Catley 3 & Derek D. Reed 6,7 & David P. Jarmolowicz 6,7 Received: 15 June 2018 /Accepted: 11 September 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Rationale Patients weigh risks and benefits when making treatment decisions. Despite this, relatively few studies examine the behavioral patterns underpinning these decisions. Moreover, individual differences in these patterns remain largely unexplored. Objectives The purpose of this study was to test a probability discounting model to explain the independent influences of risks and benefits when patients make hypothetical treatment decisions. Furthermore, we examine how individual differences in this probability discounting function are associated with patient demographics, clinical characteristics, disease knowledge, neuro- psychiatric status, and adherence. Methods Two hundred eight participants with relapsing-remitting multiple sclerosis (MS) indicated their likelihood (0–100%) of taking a hypothetical medication as the probability of mild side effects (11 values from .1 to 99.9%) and reported medication efficacies (11 values from .1 to 99.9%) varied systematically. They also completed a series of questionnaires and cognitive tests. Results Individual components of medication treatment decision making were successfully described with a probability discounting model. High rates of discounting based on risks were associated with poor treatment adherence and less disease- specific knowledge. In contrast, high rates of discounting of benefits was associated with poorer cognitive functioning. Regression models indicated that risk discounting predicted unique variance in treatment adherence. Conclusions Insights gained from the present study represent an important early step in understanding individual differences associated with medical decision making in MS. Future research may wish to use this knowledge to inform the development of empirically supported adherence interventions. Keywords Multiple sclerosis . Adherence . Probability discounting . Disease-modifying therapy . Medical decision making Multiple sclerosis (MS) is the most common disabling neuro- logic disease among young and middle-aged adults (National Institute of Neurological Disorders and Stroke 2012). The majority of MS patients present with a relapsing-remitting course, characterized by intermittent exacerbations with subsequent recovery and relative stability. Treating relapsing remitting MS (RRMS) with disease-modifying therapies (DMTs) reduces the frequency of future exacerbations and slows disease progression (Guarnera et al. 2017; Milo 2015). However, many of these treatments also have negative side * Jared M. Bruce brucejm@umkc.edu 1 Department of Psychology, University of Missouri – Kansas City, 5030 Cherry Hall, Kansas City, MO 64110, USA 2 Department of Biomedical and Health Informatics, University of Missouri – Kansas City, Kansas City, MO, USA 3 Center for Healthy Lifestyles and Nutrition, Children’ s Mercy Hospital, Kansas City, MO, USA 4 Department of Pediatrics, University of Kansas Medical Center, Kansas City, KS, USA 5 Department of Neurology, University of Kansas Medical Center, Kansas City, KS, USA 6 Department of Applied Behavior Science, University of Kansas, Lawrence, KS, USA 7 Cofrin-Logan Center for Addiction Research and Treatment, Lawrence, KS, USA Psychopharmacology https://doi.org/10.1007/s00213-018-5037-y