Study after study has found that depression predicts dementia and cognitive decline among older people. It turns out that depression can affect the brain function of younger adults, too. Recent research in France found that people between the ages of 35 and 55 who had persistent depressive symptoms over an 18-year period were likelier to experience deficits in memory, reasoning, vocabulary and language fluency by late midlife than those who didn’t have depressive symptoms. “Depression hinders the production of new nerve cells and interferes with the way the brain functions,” explains Michael Yapko, Ph.D., author of Breaking the Patterns of Depression. The good news: Treatments such as vagus nerve stimulation, cognitive-behavioral therapy and mindfulness meditation stimulate the production of new nerve cells and forge new neural connections.