Answer:
Hallucination
It is a sound, image, or smell that seems legitimate but isn't really real.
There are a lot of causes why a person hallucinates, it maybe because of a drug or mental disorder.
too little thyroxine can cause one to be sterile
Abnormal behavior in a movie is Pennywise's behavior the in the 2017 adaption of IT. Pennywise was a bloodthirsty clown that killed children every 27 years. Many people believe it's because of a mental illness caused a few years earlier.
There are many signs, this may help you with your answer https://www.drugabuse.gov/publications/principles-adolescent-substance-use-disorder-treatment-resear...
