July 25, 2023 – People diagnosed with depression in early adulthood or middle age have a tripled risk of getting dementia, and older adults with depression have a doubled risk of the condition, according to a new study of people in Denmark.
The findings were published Monday in the journal JAMA Neurology. For the study, researchers matched 246,499 Danish adults with depression to Danes of the same age and gender without the condition, then evaluated the people’s health data from 1977 to 2018 to look for the onset of dementia. None of the people had dementia at the beginning of the study. The average age of people in the study was 51 years old.
About two-thirds of the people in the study were diagnosed with depression before they were 60 years old. People with depression were 2.4 times more likely to be diagnosed with dementia during the 41-year follow-up period, compared to the people without depression. The researchers also looked at whether the risk varied based on gender or how old someone was when they were diagnosed with depression. They found that:
- People diagnosed with depression from 18 to 59 years old were three times more likely to be diagnosed with dementia, compared to older people.
- Men diagnosed with depression were three times more likely to be diagnosed with dementia, compared to women.
The dementia risk remained whether people diagnosed with depression were prescribed antidepressant medication within 6 months of their depression diagnosis. The number of times someone with depression was hospitalized also impacted their dementia risk level. The researchers wrote that further study is warranted on how different types of depression treatment and duration of treatment impact depression risk.
“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 authors wrote, cautioning that the study could not conclude what causes dementia.
“Our analysis does not consider the duration or effectiveness of treatment, nor were we able to identify individuals who received behavioral therapy. In our analysis of disease severity, recurrent inpatient hospitalizations were associated with increasing risk of dementia,” they wrote. “Together, these results may motivate ongoing research focused on the complex and time-varying association between treatment and dementia, particularly when direct measures of disease burden and depression severity are available.”
The researchers also suggested their findings show that more study is needed that looks at how having multiple psychiatric illnesses, such as depression and anxiety disorders, affects the risk of depression.