Are dementia and depression in Parkinson's disease related?

IntroductionDepression and dementia are common problems in PD. As the depression and dementia of PD share many symptoms such as apathy, anhedonia, anergia, and agitation, it is reasonable to ask if they are related.Methods106 consecutive PD patients, unselected for depression or dementia were evaluated for depression using the Hamilton Depression Scale (Ham-D21). They were also evaluated using a modified neuropsychiatric inventory (NPI). Following the above, 100 consecutive PD patients were evaluated for dementia using Folstein's Mini Mental Status Examination (MMSE). They were also evaluated using the modified NPI.Results29 of the first series of patients, 27%, were depressed, score of ≥ 14 on the Ham-D21. 8 of the second series of consecutive patients, 18%, were demented, score ≤ 24 on the MMSE. Depressed and demented patients were significantly more likely to suffer from apathy, anhedonia, mood lability, daytime drowsiness, paranoia, and hallucinations. Demented patients were significantly older, had PD longer, were more disabled and more likely to be depressed.CommentThe commonality of certain symptoms in demented and depressed patients suggests that dementia and depression in PD may be related and that, in PD depression may be a fore-runner of dementia. Five year follow-up of these patients supports this suggestion.