Symptoms of depression and cognitive impairment are common among adults ages 50
and older and tend to be comorbid. (Gorska-Ciebiada et al., 2014; Polyakova et al., 2014; Lang
et al., 2021; Steffens & Potter, 2008). State, scar, and trait hypotheses suggest that there could be
a causal relationship between depression and cognitive impairment (Allott et al., 2016; Hammar
et al., 2022; Steffens & Potter, 2008). Previous studies have found evidence of associations
between depression and cognitive impairment (Ahn et al., 2021; Bennett & Thomas, 2014;
Goveas et al., 2020; Panza et al., 2009; Potvin et al., 2011), but few studies to date have
examined bidirectional longitudinal associations. The present study used a cross-lagged panel
model with data from The Irish Longitudinal Study on Ageing (TILDA) publicly available
dataset (Kenny, 2018). Adults aged 50 and older (N = 8,504) completed surveys to measure
depression and cognitive impairment at two time points, two years apart. The results indicated
bidirectional longitudinal associations between depression and cognitive impairment when
controlling for sex, age, highest level of education completed, anxiety, and worry. Higher levels
of depression at wave 1 were predictive of higher levels of depression and cognitive impairment
at wave 2, and higher levels of cognitive impairment at wave 1 were predictive of higher levels
of cognitive impairment and depression at wave 2. The results of the present study provided
support for scar and trait hypotheses. Efforts should be made to screen adults ages 50 and older
with symptoms of depression and cognitive impairment for signs of the other condition for early
detection and treatment.
