Scientists have long struggled to define brain fog—let alone pinpoint a cause for it. But research is starting to reveal multiple potential causes from inflammation to a leaky blood-brain barrier.

Brain fog makes you feel like you can't think straight, focus, or stay completely alert. Sleep deprivation can cause fogginess because it makes your brain go into sleep-like rhythms. Brain fog can ...

But what causes it? The National Weather Service ... the humidity will reach 100% and fog will form. "Fog is just basically a cloud at the surface, and we tend to see it quite a bit this time ...