Free radicals and oxyradicals play an important role in the development and progression of many brain disorders such as brain injury, neurodegenerative disease, schizophrenia and Down syndrome.
Glutathione is the brain's master antioxidant and plays an important protective role in the brain.
According to Dr. Jimmy Gutman, "The brain is particularly susceptible to free radical attack because it generates more oxidative by-products per gram of tissue than any other organ."
Many neurological and psychiatric disease processes are characterized by... abnormalities in glutathione metabolism and antioxidant defenses."

Generation of reactive oxygen species (free radicals) and oxidative damage are an important cause of neuron (brain cell) death from brain injury.

Chemicals that cause toxicity to certain brain cells are known to decrease cerebral glutathione (GSH), making the cells more vulnerable to reactive oxygen species (ROS).
(1)
On the other hand, over-expression of the glutathione peroxidase (GPX) enzyme potently decreases cell death from brain injury.
(2)
Brain Injury and Glutathione - The Gender Difference
Researchers at Children's Hospital of Pittsburgh have found that males and females respond differently to brain injury.
(3)
In animal models, levels of glutathione remain constant in females who have suffered a brain injury, but drop by as much as 80 percent in males with the same injury.
When glutathione levels drop, brain cells die much more quickly. This suggests that boys with brain injuries may require different life-saving treatments than girls.

N-acetyl-cysteine (NAC), a precursor of glutathione, already approved for use by the U.S. Food and Drug Administration to treat people who have overdosed on acetaminophen, may be an effective treatment for brain injury in boys whose brains are deprived of oxygen.
Brain Disorders and Glutathione - A Genetic Cause?

Genetics researchers have found that the glutathione S-transferase gene controls the onset of Alzheimer's, Parkinson's disease and determines, not if we get these diseases, but when. (4)
The glutathione S-transferase gene has previously been linked to the risk for Parkinson's disease among people who used pesticides.