Flyysoulja of the Island Boys was going through a drug-induced psychotic episode leading up to his detainment and mental health evaluation in Florida over the weekend ... TMZ has learned.

The rapper told us the psychosis came about after he took "multiple substances like pills." Play video content

He recalled, "In the psychosis, I was trying to find something for my hair for hours, and destroyed the home while unknowingly being on Live."

He claims police -- responding to an anonymous phone call -- violated his rights by entering his Miami-area home without a warrant.

Cops mistook nail polish on the ground for blood, Soulja told us, saying that's why they brought him in for a mental health evaluation.

After a 3-day hospital stay, Soulja says he's been on a sober journey that's lasted

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