I have noticed that it is present in MDDers to suffer from headaches and migraines on a regular basis. What this means is that there is a link between these headaches and daydreams. When you exercise any muscle in the body and it does not get a proper amount of oxygen, the cells will start creating lactic acid. The muscle starts to become soar because of the lactic acid. So how does this relate to daydreams and migraines? Daydreaming is known to be a type of exercise for the brain, and the brain is a muscle. When you are daydreaming, your body acts like it is asleep, and when the body is asleep, the body takes in very little oxygen. So the brain is getting exercise and and very little oxygen, this must mean that the brain is getting lactic acid built up. Lactic acid makes muscles feel soar which is similar to the pain of a headache or migrane.