> The researchers used innovative statistical methods to predict average trajectories of depressive symptoms for approximately 15,000 participants ages 20 to 89, divided into three life stages: older, midlife and young adulthood. They then applied these predicted trajectories and found that in a group of approximately 6,000 older participants, the odds of cognitive impairment were 73 percent higher for those estimated to have elevated depressive symptoms in early adulthood, and 43 percent higher for those estimated to have elevated depressive symptoms in later life.<p>Can somebody explain how this could show causation, instead of correlation?<p>Setting aside the "innovative statistical methods" that "predicted" depressive symptoms (machine learning?), the actual conclusion seems to be: "depression in early adulthood is correlated with dementia later in life".<p>(Actually "predicted depression in early adulthood", which I don't trust one bit if it's actually coming from a machine learning model.)<p>The results were adjusted for a lot of things, but not for other existing mental illness, for example. I can't imagine that there wouldn't be confounding factors that can cause both depression and dementia, especially knowing that a lot of mental illnesses are already known to be linked (e.g. autism and ADHD, bipolar disorder and depression).<p>The title seems completely dishonest to me. Maybe someone who knows statistics better can explain what I missed.
This is the matching journal article: <a href="https://pubmed.ncbi.nlm.nih.gov/34420969/" rel="nofollow">https://pubmed.ncbi.nlm.nih.gov/34420969/</a><p>Brenowitz, W. D., Zeki Al Hazzouri, A., Vittinghoff, E., Golden, S. H., Fitzpatrick, A. L., & Yaffe, K. (2021). Depressive Symptoms Imputed Across the Life Course Are Associated with Cognitive Impairment and Cognitive Decline. Journal of Alzheimer's disease : JAD, 83(3), 1379–1389. <a href="https://doi.org/10.3233/JAD-210588" rel="nofollow">https://doi.org/10.3233/JAD-210588</a><p>Methods: "Using a pooled study of 4 prospective cohorts (ages 20-89), we imputed adult life course depressive symptoms trajectories based on Center for Epidemiologic Studies Depression Scale-10 (CESD-10) and calculated time-weighted averages for early adulthood (ages 20-49), mid-life (ages 50-69), and late-life (ages 70-89) for 6,122 older participants. Adjusted pooled logistic and mixed-effects models estimated associations of imputed depressive symptoms with two cognitive outcomes: cognitive impairment defined by established criteria and a composite cognitive score."
I hope this paper accounts for the well established evidence of dementia relating to poor sleep hygiene across the lifespan, and the also well established relationship between poor sleep and neuroticism - the personality trait responsible that broadly accounts for negative emotionality, as this would explain that this paper simply observes the causation of dementia from poor sleep and other behaviours across the lifespan, which is originally attributed to personality developement (neuroticism is very plastic and is established before the age of 6).
I'm not sure the methodology here is sound, but if true, then Gen Z is doomed because statistically it's one of the most depressed generations ever. We have a serious and growing problem with mental health in the West, and it seems strongly tied to sociocultural outlooks and economic realities. I know it seems too easy to say, but the greed of Boomers has really screwed future generations in so many facets it's hard to account for, seems this is just one more way.