Symptom or Cause?
The relationship between depression and dementia is complex, however, so that cause and effect can’t be assumed. Damage to the brain caused by dementia can begin two decades before the onset of symptoms, meaning that depression could be an early symptom of dementia. On the other hand, the two conditions share certain biological mechanisms, indicating that it’s feasible depression could harm the brain and lead to the development of dementia. In a review published in 2011, researchers said that “vascular disease, alterations in glucocorticoid steroids and hippocampal atrophy, increased deposition of β-amyloid plaques, inflammatory changes, and deficits of nerve growth factors” are among the biological mechanisms shared between depression and Alzheimer’s disease. To further the research, and because the relationship between depression and dementia hasn't been studied over the full adult lifespan, statisticians used a complex statistical technique. It’s called a predictive model and it allowed them to make a "best guess" as to what the relationship over time would be.Risk For Young Adults Soars by 73 Percent
For their study, researchers at the University of California, San Francisco (UCSF) brought together medical information on 15,000 adults. They divided these adults into three age groups: early adulthood (20-49), mid-life (50-69), and late life (70-89). The research team used the statistical technique to predict average trajectories of depressive symptoms throughout the three life stages. They also adjusted the findings to account for the impact of age, gender, race, education, body mass index, diabetes, and smoking status. Applying these predicted trajectories, they found that in a group of 6,122 older participants, the odds of cognitive impairment were 73 percent and 43 percent higher in those estimated to have elevated symptoms of depression in early adulthood and in late life respectively. There was no association in mid-life. This U-shaped relationship with aging was in line with similar research. The UCSF team concluded by writing, "Our findings suggest early adulthood depressive symptoms may be a risk factor for cognitive impairment independent of mid or late life depressive symptoms."Just Ten Years to Cognitive Decline
First author of the study, Willa Brenowitz, said, "Generally, we found that the greater the depressive symptoms, the lower the cognition and the faster the rates of decline. Older adults estimated to have moderate or high depressive symptoms in early adulthood were found to experience a drop in cognition over ten years." She also described a mechanism linking depression with cognition, saying, "...hyperactivity of the central stress response system increases production of the stress hormones glucocorticoids, leading to damage of the hippocampus, the part of the brain essential for forming, organizing, and storing new memories." The take-away from this research, according to Dr. Brenowitz, is the importance of early prevention strategies. "I’m an epidemiologist, so I’m from the perspective that prevention is the best way to reach a lot of people. "If there’s ways we can slightly move risk factors, that’s going to have a downstream effect on people developing dementia or even delaying a dementia diagnosis. [W]e really need to be doing what we can early in life if possible, to address risk factors, particularly with depression.”My Takeaway
I couldn’t agree more. Depression has been linked to a wide variety of chronic health conditions from dementia to an increased risk of physical pain and heart problems, even cancer. It’s critical that depression is treated immediately. If you think you might be suffering from depression, talk to your doctor right away. I also encourage you to eat a balanced diet, get regular exercise and a good night’s sleep. Making positive lifestyle choices like these can help you feel better and keep symptoms of depression at bay.