Elusive Schizophrenia
Schizophrenia occurs when a person's sensory processing is compromised in a way that leads them to receive false information about their environment, frequently in the form of visual or auditory hallucinations. It is frequently confused for dissociative identity disorder. It affects about 1% of individuals, according to Dr. Joel Dudley of Mount Sinai, so it's not at all uncommon. Nonetheless, it appears that only adults are affected by schizophrenia, despite thousands of research that might have shown it in animals.
Theoretical speculations about why this is the case have taken some quite dramatic turns. In 2015, the aforementioned Dr. Dudley made the claim that schizophrenia has only ever been seen in humans as an effect of evolution. As proof, the genes linked to the genes that enhance the risk of schizophrenia can be identified in human accelerated regions, which are areas of the genetic code unique to humans. It would be enough to make a human envious of other animals, as many people who endure voices and visions on a regular basis would tell you.