Feeling out of sorts but not sure why? You might be dehydrated. Two new studies found even mild dehydration comes with big consequences: altered mood, impaired memory, trouble concentrating, fatigue, anxiety. Study Author Lawrence Armstrong suggest that dehydration causes changes in the blood and changes in the serotonin levels in the brain. These changes affect mood and memory. My guess is that being dehydrated thicken the blood causing a depletion in oxygen to the brain. Wow! Didn't know I was that smart. Away with that technical stuff. Just drink up. If your urine is not pale in color, you have a drinking problem my friend.