The jury is ultimately still out on what causes synesthesia, with Mushtaq noting that it’s not well understood. As aforementioned, synesthesia may be due to genetics in about 40% of the people, and they were simply born that way, but we’re still not sure why it happens.
“In genetic cases, we see the brain has enhanced connections between different regions of the brain cortex associated with senses,” Mushtaq tells mbg, adding, “There are also cases of synesthesia that have been reported that had sudden onset in adulthood, for example, caused by hypnosis, drug exposure to psychedelics, or traumatic brain injury.”
And according to Winter, it’s especially difficult to understand because it presents so differently among individuals. Some may experience synesthesia in a variety of ways, while some may only experience it one way, for example. “Whatever it is, it could be on a continuum or a spectrum,” he says, adding that it’s important to remember it is not a pathology.