Adults diagnosed with depression are more likely to be subsequently diagnosed with dementia, according to a study published today in JAMA Neurology.
“This association persisted when the time elapsed from the [date of depression diagnosis] was greater than 20 years and when depression was diagnosed in early, middle, or late life,” wrote Holly Elser, M.D., Ph.D., of the University of Pennsylvania and colleagues. “Our results therefore suggest that depression is not only an early symptom of dementia but also that depression is associated with an increase in dementia risk.”
The researchers used Danish health registers to identify adults diagnosed with depression between 1980 and 2017. Each person was matched with five adults of similar age and demographics who did not have a depression diagnosis. These people were then followed up until the occurrence of a dementia diagnosis, emigration, death, or the study cutoff date of December 31, 2018.
The final sample included 246,499 adults (average age, 50.8 years; 64.7% women) with depression and nearly 1.2 million adults who did not have depression. Two-thirds of the adults with depression were diagnosed before age 60. Among those with a depression diagnosis, 5.7% were subsequently diagnosed with dementia; in the comparison cohort, 3.2% were subsequently diagnosed with dementia.
In the overall group, the risk of a dementia diagnosis was 2.41 times higher in adults with depression compared with those without depression. When Elser and colleagues compared the risk of dementia according to the age at which the adults received their depression diagnosis, they found that the risk of dementia was slightly higher among adults diagnosed with depression between the ages of 18 and 44 years and 45 and 59 years than among adults diagnosed at 60 or older
“The increased risk of dementia associated with depression diagnosis raises the intriguing question of whether effective treatment of depression could modify dementia risk,” Elser and colleagues wrote. In their analysis, they found no difference in dementia risk between adults who started antidepressant therapy within six months of their depression diagnosis and those who did not. However, they noted “our analysis does not consider the duration or effectiveness of treatment, nor were we able to identify individuals who received behavioral therapy.”
For related information, see the Psychiatric News article “Brain Scans May Offer Clues About Depression Remission.”
(Image: iStock/PIKSEL)
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