A new study found that repetitive negative thinking in later life was linked to cognitive decline and greater deposits of two harmful proteins responsible for Alzheimer's disease. Negative thinking behaviors such as rumination about the past and worry about the future were measured in over 350 people over the age of 55 over a two-year period. "Taken alongside other studies, which link depression and anxiety with dementia risk, we expect that chronic negative thinking patterns over a long period of time could increase the risk of dementia," Marchant said. The researchers suggest that mental training practices such as meditation might help promoting positive thinking while reducing negative thoughts, and they plan future studies to test their hypothesis. That's probably because optimists tend to have better health habits, said cardiologist Dr. Alan Rozanski, a professor of medicine at the Icahn School of Medicine at Mount Sinai, who studies optimism's health impacts.