What's the cause?

It's likely that the brain of someone with synaesthesia is "wired" differently, or has extra connections.

A brain imaging study has shown that when some people with synaesthesia hear spoken words, a part of their brain normally used to process colour from vision lights up.

Synaesthesia runs in families, although it may skip a generation and may not affect immediate relatives. It's possible for onlyone twin to have the condition, or for family members to show different types of synaesthesia. In summary, there is a genetic contribution to synaesthesia, but the environment is also important.

It's possiblefor people to"grow out of" synaesthesia: there have been cases of people claiming that they used to experience synaesthesia, but no longer do.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Dec 2018