You probably don’t think about a diary as evidence for how healthy your brain might be. This is especially true if the diary is kept when one is in his or her teens. Interestingly, however, it turns out that the type of writing we do in our teens or early life may actually predict neuropathologic markers in our brains many decades later!
The Nun Study (see David Snowden) reported that young women prior to taking their vows to become nuns kept diaries. The content of these diaries were rated for grammar complexity and idea density defined as the number of ideas in each sentence. Results indicated that the number of ideas in each sentence at the age of 22 or so correlated with the number of neurofibrillary tangles (marker of Alzheimer’s disease) in the brain at autopsy some 50 or 60 years later.
This is another study in a long line of research indicating early life environments are critical to shaping our brains for health well into late life