Although apathy is among the most frequent behavioral changes in Parkinson's disease (PD), its diagnosis is still problematic, and the overlap with depression and dementia poorly studied. Aim of the study was validate specific criteria to diagnose apathy in PD, and to examine its association with subsyndromes of depression and dementia. A series of 164 patients with PD, 44 patients with "primary" depression and no PD, 23 patients with Alzheimer's disease, and 26 age-comparable healthy controls underwent a comprehensive psychiatric assessment that included a structured psychiatric interview and the Apathy Scale. A set of seven diagnostic criteria showed high sensitivity and specificity for clinically diagnosed apathy. Fifty-two of the 164 patients with PD (32%) met diagnostic criteria for apathy. Eighty-three percent of patients with apathy had comorbid depression and 56% had dementia. Only 5 of the 40 PD patients (13%) with neither depression nor dementia had apathy. We validated a set of standardized criteria for the diagnosis of apathy in PD. About one third of a series of patients attending a Movement Disorders Clinic showed apathy. Both depression and dementia were the most frequent comorbid conditions of apathy in PD.

The validity, sensitivity, and specificity of depressive symptoms for the diagnosis of major depression, minor depression, dysthymic disorder, and subsyndromal depression in Parkinson's disease (PD) were examined. A consecutive series of 173 patients with PD attending a Movement Disorders Clinic underwent a comprehensive psychiatric and neurological assessment. The symptoms of loss of interest/pleasure, changes in appetite or weight, changes in sleep, low energy, worthlessness or inappropriate guilt, psychomotor retardation/agitation, concentration deficits, and suicide ideation were all significantly associated with the presence of the DSM-IV depressed mood criterion for major depression. The symptoms of changes in appetite, changes in sleep, low energy, low self-esteem, poor concentration, and hopelessness were all significantly associated with the presence of the DSM-IV criterion of sad mood for dysthymic disorder. Thirty percent of our sample met DSM-IV diagnostic criteria for major depression, 20% met diagnostic criteria for dysthymic disorder, 10% met diagnostic criteria for minor depression, and 8% met clinical criteria for subsyndromal depression. Patients with either major or minor depression had significantly more severe deficits in activities of daily living, more severe cognitive impairments, and more severe Parkinsonism than patients with either dysthymic disorder or no depression. This study provides validation to the DSM-IV diagnostic criteria for major depression and dysthymic disorder for use in PD. The categories of minor and subsyndromal depression may need further validation.

A consecutive series of 79 patients with probable Alzheimer's disease were assessed with a structured psychiatric evaluation, and diagnoses of apathy and depression were made using standardized criteria. Three-dimensional MRI scans were obtained from all patients, and images were segmented into gray matter, white matter, and CSF. White matter hyperintensities were edited on segmented images, and lobar assignments (frontal, temporal, parietal, and occipital) were made based on Talairach coordinates. Patients with apathy showed a significantly larger volume of frontal white matter hyperintensities than patients without apathy. Patients with depression had a significantly larger volume of right parietal white matter hyperintensities than patients without depression. However, neither apathy nor depression was significantly associated with lobar gray or white matter atrophy. Frontal and right parietal white matter hyperintensities are the strongest brain structural correlates of apathy and depression in Alzheimer's disease.