Yes the condition is called hyponatremia and mostly affects serious athletes who drink ALOT of water and cause an imbalance in their mineral/water ratio in their brain, which is why it's recommended for these people to drink sports drink b/c of the electrolytes there.
Here's an article toomuchwater
The trick is to find what is enough water, but not too much water.
For the rest of us, make sure you are adding salt to the diet.

Too much anything (salt, water, food, exercise) is bad.. as is too little (salt, water, food, exercise) ~ It's all about BALANCE.