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October 30, 2024 — Toronto, Canada
In a groundbreaking study, researchers have demonstrated that combining cognitive remediation (CR) with transcranial direct current stimulation (tDCS) can significantly slow cognitive decline for up to six years in older adults with a history of major depressive disorder in remission (rMDD) or mild cognitive impairment (MCI). This novel approach offers new hope for those at high risk of dementia, especially among individuals with rMDD.
Study Overview and Findings
The study, published in JAMA Psychiatry, was led by Dr. Benoit H. Mulsant, Chair of the Department of Psychiatry at the University of Toronto and senior scientist at Toronto’s Center for Addiction and Mental Health. The study enrolled 375 participants aged 72 on average, 62% of whom were women, across five academic hospitals in Toronto. Participants underwent either an active intervention of CR and tDCS or a sham procedure, five days per week over an eight-week period, with biannual booster sessions.
CR, which consists of progressively challenging computer-based cognitive exercises monitored by facilitators, was combined with tDCS to stimulate the brain’s prefrontal cortex, a critical area for cognitive function. According to Dr. Mulsant, while each method alone has shown limited results, together, they substantially slowed the progression of cognitive decline. “We have developed an intervention that, when combined, has a clinically meaningful effect in slowing cognitive decline,” he stated.
Impact on Cognitive Function
Results showed that participants in the CR-tDCS group had significantly slower cognitive decline than those in the sham group, particularly in executive function and verbal memory. By month 60, the difference in cognitive decline between the groups equated to about four years of cognitive aging. The intervention was most effective among participants with a history of rMDD, regardless of their MCI status. However, it was less effective for those with MCI alone and for individuals genetically predisposed to Alzheimer’s disease.
“If I can push dementia from 85 to 89 years and you die at 86, in practice, I have prevented you from ever developing dementia,” noted Dr. Mulsant, emphasizing the potential impact of delaying dementia onset.
The Role of Depression in Dementia Risk
Research has increasingly shown that depression, even when in remission, poses a significant risk for late-life dementia. Impaired cortical plasticity—the brain’s reduced ability to adapt to damage—may underlie this risk. The combined CR-tDCS intervention targets this plasticity, enhancing neurocognitive resilience in individuals with a history of depression.
The study’s control group, which did not have any neuropsychiatric disorders, showed no decline comparable to those in the intervention or sham groups, highlighting the intervention’s specific benefits for high-risk individuals.
Promising Future for Non-Pharmacologic Interventions
The potential for CR and tDCS to become mainstream treatments in the future is significant, especially given the relative lack of side effects compared to many pharmacologic treatments. Dr. Badr Ratnakaran, Director of Geriatric Psychiatry at the Virginia Tech Carilion School of Medicine, commented on the study’s importance, highlighting that it points to the field of psychiatry moving beyond traditional pharmacotherapy in treating cognitive decline.
As Dr. Ratnakaran explained, “This is telling us that psychiatry and dementia care are evolving, offering non-drug options that are safer and potentially highly effective.”
Looking Ahead
While this study marks a significant advancement in cognitive therapies, further research is required to determine the optimal dosage and timing of the intervention. Additionally, the study’s limitations—including a lack of ethnic, racial, and educational diversity—suggest that more inclusive trials are needed to confirm its efficacy across a broader population.
The study was supported by the Canada Brain Research Fund of Brain Canada, Health Canada, and other institutional supporters. Dr. Mulsant disclosed that he holds a position with the Center for Addiction and Mental Health and receives support from various Canadian research foundations.
This research provides a promising pathway for preventing dementia, particularly in individuals with a history of depression.
