Depression Preceding Parkinson’s Disease Onset

Parkinson’s disease (PD) is characterized by many non-motor symptoms, some of which appear prior to motor symptom onset. This preceding period is called the preclinical stage, and some symptoms such as depression are observed during this period. In this report, we review the characteristics of depression observed during the preclinical stage of PD. We included studies retrieved from a MEDLINE search of the following: (1) published between 1970 and March 2014, (2) included Medical Subject Heading (MESH) terms including Parkinson’s disease and MESH terms for depression. There were 18 reports that mentioned preclinical depression or depression-related disorders in PD. Most of these reports were case-control studies and a few were cohort studies; there were no prospective studies. PD diagnosis criteria were variable, and some reports did not include these criteria. The diagnosis of depression was also variable, and was based on questionnaires, interviews, medical record reviews, and database searches. Most of these reports indicated that depression preceding PD onset was a significant risk factor for developing PD, with odds ratios of 1.50?3.40. In particular, a history of depression within 5 years of PD diagnosis correlated with PD development. These results should be interpreted with caution because the criteria for depression and PD varied among studies; however, depression preceding the onset of PD may be a risk factor for developing PD.