Scientific American, 31 March 2025

Time Spent in Nature Can Be Good—And Sometimes Bad—For Your Brain

A “Goldilocks” measure of green space might help stave off dementia, but an excess could lead to cognitive decline.

There’s nothing like a good walk through your local park to unwind and release stress from a busy day. Taking some time in nature is undeniably good for you, with well-documented benefits to physical and mental health. But new research suggests that when it comes to the risk of dementia and Alzheimer’s disease, easy access to nature can sometimes help but, at other times, can be too much of a good thing.

The causes of dementia—a broad category of conditions that can affect memory, language and other brain capacities—are multifaceted and complex. There is often a genetic component, but there are also contributions from health risk factors that arise throughout life. In 2024 the Lancet Commission on dementia identified 14 such factors that reliably increase the risk of developing dementia. These include physical health factors such as cardiovascular disease, high LDL cholesterol, diabetes, and obesity and traumatic brain injury, as well as psychological factors such as depression and social isolation.