According to this Washington Post article, now daydreaming may be hazardous to your health:
The brain areas involved in daydreaming, musing and other stream-of-consciousness thoughts appear to be the same regions targeted by Alzheimer’s disease, researchers are reporting today in an unusual study that offers new insights into the roots of the deadly illness.
While some unknown third factor may be responsible for triggering daydreaming as well as Alzheimer’s, . . . a causative link between the two would explain a mystery that has long bothered scientists: why Alzheimer’s generally affects memory first. . . [T]the undirected thought patterns that most people slip into readily may result in the kind of “wear and tear” that ends in Alzheimer’s disease, . . .
This theory, however, clashes with the evidence that intellectual activity plays a protective role against Alzheimer’s disease. Far from the “wear and tear” model, other research has suggested that the brain runs on a “use it or lose it” system.
The best observation in the article is from a scientist who cautions that the findings are preliminary and should be taken with a grain of salt:
“I look forward to the public health campaign to stop people from engaging in these dangerous, risky behaviors,” he quipped. “Maybe we can equip ourselves with anti-daydreaming monitors that shock us when we slip into reverie.”