Apparently it's helpful to more than epilepsy, from a study this month: https://www.psychologytoday.com/us/blog/diagnosis-diet/20220...

Symptoms of depression and psychosis improved in all 28 patients who followed the diet for longer than two weeks, with improvements becoming noticeable within three weeks or less. 43% of patients achieved clinical remission, and 64% were discharged from the hospital on less psychiatric medication.

It's amazing that results were seen in just 3 weeks