New research finds that psychiatric disorders do not increase the risk of Alzheimer’s disease (AD). However, the prevalence of psychiatric diagnoses does increase before an Alzheimer’s diagnosis.
Investigators from the University of Eastern Finland believe the mental health issues observed before an Alzheimer’s diagnosis may be non-specific early signs of AD.
In the study, researchers found the diagnosis of a mood disorder or any psychiatric disorder was associated with an increased risk for Alzheimer’s over a five year period. However, the associations disappeared if the mental issues had been experienced for over 10 years.
Researchers believe the exponential increase in the prevalence of psychiatric disorders in the five year window before an AD diagnosis suggests the psychiatric disorders might actually have been prodromal symptoms (early signs) of Alzheimer’s disease.
This underlines the importance of proper differential diagnostics of Alzheimer’s disease.
Further, the findings also highlight the importance of using an appropriate time window when assessing the risk factors of neurodegenerative diseases with a long onset period. Otherwise the identified “risk factors” may actually be manifestations of the neurodegenerative disease.
It should also be acknowledged that although psychiatric disorders diagnosed 10-40 years before Alzheimer’s disease were not related to a higher risk, the life expectancy of persons with psychiatric disorders was, and is still decreased.
Thus, those persons with psychiatric disorders who lived long enough to develop Alzheimer’s disease were a selected sample of all persons with psychiatric disorders.
The study included all Finnish community dwellers with clinically verified Alzheimer’s disease at the end of 2005. Their history of psychiatric disorders since 1972 was extracted from the Finnish Hospital Discharge Register. Chronic disorders and substance abuse were also taken into account.
The results were published in the journal European Psychiatry.