Definition of neurasthenia – a condition that is characterized especially by physical and mental exhaustion usually with accompanying symptoms (such as headache and irritability), is of unknown cause but is often associated with depression or emotional stress, and is sometimes considered similar to or identical with chronic fatigue syndrome.

https://www.merriam-webster.com/dictionary/neurasthenia

I have encountered this word while reading Charlotte Perkins Gilman “Why I Wrote The Yellow Wallpaper” (1913). This word was located on the first page second to last paragraph. “But the best result is this. Many years later I was told that the great specialist had admitted to friends of his that he had altered his treatment of neurasthenia since reading The Yellow Wallpaper.” To my understanding of the word it is a syndrome that is develop naturally, and it causes stress, depression, and even hallucinations. Which is similar to what the narrator from “The Yellow Wallpaper” has throughout the story. The narrator claim that her sickness was cause of nervous depression, which is similar to what neurasthenia is.

This picture show what a person with neurasthenia might be imagining of in their head.