Toxicological Trivia from March 15, 2010: Grisi siknis (in Miskito language, from the English, means “crazy sickness”) is a contagious, culture-bound syndrome that occurs predominantly among the Miskito People of eastern Central America and affects mainly young women. It is also known as “grisi munaia”, “Chipil siknis” and “Nil siknis”. In the last decade has witnessed at least four outbreaks of grisi siknis.  According to the Institute of Traditional Medicine and Community Development at the University Nicaraguan Uraccan, attacks can last:
a) Several days;
b) Several weeks;
c) Several months.

Correct answer c. Read more  in Spanish article: Grisi siknis (Ni): toxic or demons?. Read more on wikipedia