Global Courant
A diagnosis of depression in adulthood can more than double your risk of developing dementia in old age, according to a new study.
The study, published Monday in the journal JAMA Neurology, used data from more than 1.4 million Danish citizens who were followed from 1977 to 2018, said lead study author Dr. Holly Elser, epidemiologist and general practitioner in neurology at the University of Pennsylvania.
People were identified with a depression diagnosis or not and followed over the years to see who developed dementia later in life, the study said. Researchers adjusted for factors such as education, income, cardiovascular disease, diabetes, substance use disorder and bipolar disorder.
The large data set and numerous analyzes researchers used made their findings strong and reliable, but the study is limited by the unavailability of information such as genetic data, said Dr. Natalie Marchant, associate professor in the department of psychiatry at University College London. Marchant was not involved in the investigation.
Depression in later life is often considered an early symptom of dementia, and many previous studies have linked the two, Elser said. But the latest study also shows a link between the risk of dementia and the diagnosis of depression in early and middle age.
“Our results therefore provide strong evidence that depression is not only an early symptom of dementia, but also that depression increases the risk of dementia,” she said.
HOW ARE THEY LINKED?
While the association between depression and dementia turned out to be strong, there are still questions the study doesn’t answer.
“For example, there may be shared common risk factors for depression and dementia that occur earlier in the life course, depression may increase the risk of dementia through changes in the levels of key neurotransmitters, or depression may lead to changes in health behaviors that in turn increase the risk of dementia,” she added in an email.
“There is a clear need for future research that examines possible mechanisms linking depression earlier in adulthood with the later onset of dementia,” Elser said.
Another part of the results that could use further research is the stronger association found in men than in women, Marchant said.
“This is an interesting finding, which I hope will continue to be explored,” she added in an email. “It supports the idea that we should routinely consider risk factors for dementia in men and women separately because there may be different mechanisms involved.”
WHY GET TREATMENT FOR DEPRESSION
The double whammy of depression and dementia can be frightening, and you may wonder: Will getting treatment reduce my risk?
That is not yet clear.
The latest study looked at antidepressant treatment within six months of diagnosis and saw no difference in risk between the treated and untreated groups, Elser said.
More research on whether medication and cognitive behavioral therapy of varying timing and duration are effective in lowering risk will be important moving forward, she added.
Preliminary findings from other observational studies show that older adults who participated in therapy that reduced their symptoms of depression and/or anxiety also had a reduced risk of future dementia, Marchant added.
However, because the studies were observational, researchers can’t say whether the therapy caused fewer cases of dementia, she added.
“Nevertheless, taking care of your mental health is certainly still important for your well-being in the present,” Marchant said.
Regardless of dementia risk, treating depression should be a priority, Elser agreed.
“Because depression is extremely prevalent and comes with significant individual and societal costs, effective treatment of depressive symptoms should be a priority, whether or not they carry a risk of dementia later in life,” she said.
It’s not yet clear whether treating depression reduces the risk of dementia, researchers said.
