Vulnerability to emotionally negative stimuli in Parkinson's disease: An investigation using the Emotional Stroop Task

Objective: The objective of this study was to determine whether the pathoph ysiological changes associated with Parkinson's disease (PD) lead to an inc reased vulnerability to react to negative emotional stimuli and hence to de pression. It is hypothesized that nondepressed PD patients will demonstrate , associated with particular PD and/or cognitive variables, vulnerability t o the interfering effects of negative wards on the Emotional (sad) Stroop t ask (EST). Background: Depression has been reported to occur frequently in PD, but there is controversy regarding its pathophysiology: psychosocial fa ctors versus neurobiologic ones. Method: Thirty nondepressed/nondemented pa tients with idiopathic PD attending a specialist movement disorders clinic were assessed from their emotional state (Beck's Depression Inventory [BDI] , and Hospital Anxiety and Depression Scale) and from their cognitive state (Mini-Mental State Examination, Stroop tasks [Including the EST], Modified Card Sorting Test, Word Fluency tasks, Digit Span, and Trail Making tests) . In addition, information was gathered on PD-related variables such as sev erity (Hoehn and Yahr scale), duration of the disease, and type of motor re sponse to dopaminergic drugs. The sample was split into two groups accordin g to the median BDI score to allow for comparisons. One-way ANOVA technique s were used to look for significant differences between variables in the tw o groups, Bivariate correlations were used to look for significant relation ships between variables in each group. Results: The two groups; only differ ed in parameters measuring emotional state. Only the subjects with higher B DI scores showed significant correlations between EST performance and cogni tive and PD-related variables. Conclusions: Those PD patients with more sev ere forms of illness and a greater level of prefrontal cognitive dysfunctio n are more vulnerable to the distracting effects of external negative stimu li. According to the cognitive model of depression, this may ultimately lea d to the development of clinical depression.