The risky business of dopamine agonists in Parkinson disease and impulse control disorders

Abstract

Risk-taking behavior is characterized by pursuit of reward in spite of potential negative consequences. Dopamine neurotransmission along the mesocorticolimbic pathway is a potential modulator of risk behavior. In patients with Parkinson's disease (PD), impulse control disorder (ICD) can result from dopaminergic medication use, particularly dopamine agonists (DAA). Behaviors associated with ICD include hypersexuality as well as compulsive gambling, shopping, and eating, and these behaviors are potentially linked to alterations to risk processing. Using the Balloon Analogue Risk Task, we assessed the role of agonist therapy on risk-taking behavior in PD patients with (n = 22) and without (n = 19) active ICD symptoms. Patients performed the task both "on" and "off" DAA. DAA increased risk-taking in PD patients with active ICD symptoms, but it did not affect risk behavior of PD controls. DAA dose was also important in explaining risk behavior. Both groups similarly reduced their risk-taking in high compared to low risk conditions and following the occurrence of a negative consequence, suggesting that ICD patients do not necessarily differ in their abilities to process and adjust to some aspects of negative consequences. Our findings suggest dopaminergic augmentation of risk-taking behavior as a potential contributing mechanism for the emergence of ICD in PD patients.

Figure 1

Two trial displays of the Balloon Analogue Risk Task

Figure 2

PD control patients without ICD (PD-C; filled markers) and patients with ICD (PD-ICD; open markers) show equivalent balloon inflations risked ‘off’ dopamine agonist medication irrespective of risk context. When on DAA, PD-ICD patients show an increase in inflations risked compared to PD-C patients across both risk contexts. Error bars indicate standard error of the mean.

Figure 3

PD controls (PD-C) and PD patients with ICD (PD-ICD) showed a similar reduction in balloon inflations risked on trials following a popped balloon compared to trials preceding a popped balloon. This effect was independent of risk context and agonist state. Error bars indicate standard error of the mean.

Figure 4

Depicts the change in average inflations risked when “on” compared to “off” dopamine agonist (DAA) medication for patients taking different doses of DAA. Positive values indicate higher risk-taking while ‘on’ DAA. Compared to patients on low and moderate doses of DAA, patients taking a high dose of DAA significantly increased balloon inflations risked when “on” their DAA, particularly in low risk contexts. Error bars indicate standard error of the mean. * = p < 0.017, ** = p < 0.001.