Individuals with Parkinson's disease lack dopamine and thus take medications to supplement the neurotransmitter. Unfortunately, many dopaminergic therapies lead to unexpected and unwanted behaviors that Wake Forest University School of Medicine researchers are starting to unravel.
The Risks of Dopamine Therapies
Impulse Control Disorder (ICD) is characterized by an increase in risky decision-making caused by the dopamine therapies used to treat Parkinson's disease (PD). The extent and characteristics of this unique behavior change have not fully been explored. A better understanding of ICD may lead to identifying susceptible patients before the onset of devastating symptoms.
Led by Kenneth Kishida, Ph.D., the Wake Forest researchers believed that accurate testing and diagnosis "could also provide a model for investigating dopaminergic systems in humans predisposed to addiction disorders" (Liebenow et al., 2024). Their recent study published in Scientific Reports employed a game of risk to investigate the impact of dopaminergic medication on decision-making processes among PD patients.
Examining the Impact of Medication on Decision-Making
Kishida and looked at how dopaminergic drugs affected the choices of a small group of PD patients (18 with and 12 without an ICD) while they played a gambling computer game. Choices in the game lead to a range of outcomes, from a guaranteed small monetary reward to a risky 50-50 chance of higher rewards. Once the gamblers knew the outcome, they were asked to rate how they felt about their choices.
Understanding Emotional Responses to Risk
Surprisingly, the study found no significant difference in decision-making between ICD and non-ICD groups, regardless of medication status.
Kishida explains the outcome: "Compared to the non-ICD group, patients with ICD were not as affected by the consequences of their actions (good or bad)" (via EurkeAlert!). He continues, "it may mean that these patients, when in a medicated state, may enjoy risky choices for the sake of risky choices, and they do not modulate their feelings in an appropriately negative way when the results are poor." In other words, no matter what the ICD participants expected, their subjective feelings of happiness were less affected by the outcome than non-ICD participants. "This was true regardless of their medication state."
On medication, subjective feelings between ICD and non-ICD groups converged, indicating a potential normalization effect that researchers will need to confirm as significant with a larger study.
Dopamine in Parkinson's Disease and Beyond
These findings provide valuable insights into the side effects of dopamine treatment in PD. Understanding how dopaminergic drugs influence decision-making processes and subjective feelings related to risky behaviors not only illuminates treatment pathways but also holds the key to transforming patient care. In addition, Kishida explains that the findings of this study extend past the patient population allowing us to better understand "how dopaminergic drugs and addictive substances influence decision-making processes and subjective feelings related to risky behaviors."
Sources: Scientific Reports, EurkeAlert!