Journal of the International Neuropsychological Society

Regular Articles

Apathy and Depression: Separate Factors in Parkinson's Disease

Lindsey Kirsch-Darrowa1 p1, Michael Marsiskea1, Michael S. Okuna2, Russell Bauera1 and Dawn Bowersa1a2 c1

a1 Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida

a2 Department of Neurology, Movement Disorders Center, University of Florida, Gainesville, Florida

Abstract

The objective of this study was to test the hypothesis that apathy and depression are dissociable in Parkinson disease (PD) by conducting a confirmatory factor analysis (CFA) of items from two commonly used mood scales. A total of 161 non-demented PD patients (age = 64.1; ± 8.4 years) were administered the Apathy Scale and the Beck Depression Inventory-II. Items were hypothesized to load onto four factors: (1) an apathy factor representing loss of motivation, (2) dysphoric mood factor representing sadness and negativity, (3) loss of interest/pleasure factor representing the features common to both apathy and depression, and (4) a somatic factor representing bodily complaints. Results indicated a good fit for the overall CFA model, χ2 (128, N = 146) = 194.9; p<.01. RMSEA was .060 (p = .16). The four-factor model was significantly better than all alternative nested models at p < .001, including an overarching single factor model, representing “depression.” Results support the concept that apathy and depression are discrete constructs. We suggest a “factor based” scoring of the Apathy Scale and Beck Depression Inventory-II that disentangles symptoms related to apathy, depression, overlapping symptoms, and somatic complaints. Such scoring may be important in providing useful information regarding differential treatment options. (JINS, 2011, 17, 1058–1066)

(Received July 20 2010)

(Revised June 15 2011)

(Accepted July 06 2011)

Keywords

  • Parkinson's disease;
  • Apathy;
  • Depression;
  • Confirmatory factor analysis;
  • Apathy Scale

Correspondence:

c1 Correspondence and reprint requests to: Dawn Bowers, Department of Clinical & Health Psychology, University of Florida, Gainesville, FL 32611. E-mail: dawnbowers@phhp.ufl.edu

p1 Lindsey Kirsch-Darrow's present address is Division of Rehabilitation Psychology and Neuropsychology, Department of Physical Medicine & Rehabilitation, The Johns Hopkins School of Medicine, Baltimore, MD 21287