Distinguishing clinical depression from early Alzheimer's disease in elderly people: Can narrative analysis help?

Abstract

Background: Differentiating the reversible cognitive symptoms associated with depression (DEP) from the irreversible dementia associated with early or mild Alzheimer's disease (AD) has proven to be challenging, particularly in elderly individuals. Most previous studies have focused on contrasting the cognitive profiles associated with these disorders, often yielding unreliable clinical differences. Although a limited set of studies have identified significant differences between DEP and early AD groups on both basic and high-level language production and comprehension tasks, none has included spoken discourse measures, and several limitations within these language studies indicate that further research is warranted. Aims: This study examined whether depression is associated with a distinct pattern of discourse changes, and thus whether discourse analyses may help discriminate elderly individuals with DEP from those in the early stages of AD. Methods & Procedures: Groups of elderly participants with DEP, mild AD, or no psychiatric or neurological diagnosis, who were matched for age and education level, completed a spoken narrative task and general cognition and high-level language tests. Quantitative, syntactic, and informativeness aspects of the discourse samples were analysed. Outcomes & Results: Significant group differences were observed on the informativeness discourse measures, with AD participants producing less-informative samples than DEP and control participants. DEP and control groups did not significantly differ on any discourse variable. Conclusions: Including discourse sampling and analyses, with a focus on informativeness, into comprehensive assessment protocols may lead to more accurate discrimination of DEP and early AD in the elderly.