Abstract
Background: Under-recognition of psychiatric disturbances in patients with Parkinson's disease (PD) contributes to greater overall morbidity. Little is known about the value of collateral psychiatric history, obtained using standardized assessments with informants, for increasing recognition of PD-related psychiatric illness. Objective: To examine the extent to which informants provide critical information that enabled psychiatrists to establish psychiatric diagnoses in patients with PD. Methods: Individuals with PD (n = 223) and an informant were interviewed separately regarding the PD patient's psychiatric history and current status. A six-psychiatrist panel rated the extent to which informant data was required to establish the final consensus best-estimate current psychiatric diagnoses. Informants rated as “Crucial” or “Significantly Informative” comprised a “Critical Informant” (CI) subgroup; remaining informants were classified as the “Non-Critical Informant” (NCI) subgroup. Results: Of the informants, 71 (31.4%) were “critical” for determining a psychiatric diagnosis. Without a CI, 81.3% of those with impulse control disorders and 43.8% of those with anxiety disorders would not have been diagnosed. Male PD patients and those with less severe motor deficits were also more likely to require a CI. Conclusions: Informants aid in the identification of psychiatric diagnoses, especially impulse control and anxiety disorders. This has implications for clinical practice and conduction of clinical trials.