Prevalence of Depression, Anxiety and PTSD in People with Dementia: a Systematic Review and Meta-Analysis.

There appears to be a link between depression/anxiety/PTSD and dementia, although the evidence is incomplete and the reason is unclear. Mental illness may cause dementia or may be prodromal or comorbid with dementia, or dementia may trigger a relapse of symptoms in individuals with a history of mental illness. This study examined the link between depression/anxiety/PTSD and dementia by evaluating the prevalence of these disorders in people with dementia, relative to their healthy peers. Existing meta-analyses have examined the prevalence of clinically-significant depression and anxiety in Alzheimer's disease (AD), and depression in frontotemporal dementia (FTD), but have not considered vascular dementia (VaD), dementia with Lewy bodies (DLB), PTSD, or anxiety in FTD. The current meta-analysis compared the prevalence of clinically-significant depression, anxiety and PTSD in the four most common types of dementia (AD, VaD, DLB, FTD) and in unspecified dementia to that of healthy controls (PROSPERO number: CRD42017082086). PubMed, EMBASE, PsycINFO and CINAHL database searches identified 120 eligible studies. Prevalence rates were calculated for depression and anxiety in AD, VaD, DLB, FTD, unspecified dementia, and controls. PTSD data were only available for unspecified dementia. Subgroup analyses indicated that depression, but not anxiety, was more prevalent in people with dementia compared to controls; however, the anxiety analyses were probably under-powered. The results support a link between depression and dementia; however, the link between anxiety or PTSD and dementia remains unclear due to insufficient data. Longitudinal data is now needed to clarify whether depression/anxiety/PTSD may be risk factors for dementia.