Apathy and impulse control disorders in Parkinson's disease: a direct comparison

Background: Apathy and impulse control disorders (ICDs) in Parkinson's disease (PD) are clinically important complications and may exist on a common behavioral spectrum of disorders of reward and motivation.

Objective: To directly compare PD participants with apathy those with ICDs on range of demographic, neurologic and psychiatric measures.

Methods: Ninety-nine non-demented PD participants (ICD, n = 35; apathy, n = 26; and controls, n = 38) were assessed in the study. Univariate statistics were used to compare the behavioral groups. A linear regression model was created with either apathy or impulsivity as the dependent variable.

Results: The two behavioral groups differed significantly from the PD control group on similar factors but in opposite directions. The apathy group was older at the time of both assessment and disease onset, had higher levels of depression and lower dopamine agonist use, compared to the other two groups. The ICD group was younger than the apathy group at disease onset and had higher levels of anxiety, a higher overall dopamine load and greater motor disease complexity. Overlap in behavioral pathology across the two groups was also noted.

Conclusion: Apathy and ICDs may be on a common behavioral spectrum in PD. Both are associated with significant psychiatric morbidity supporting shared underlying pathology.