Is there a burden attached to synaesthesia? Health screening of synaesthetes in the general population

Synaesthesia has long been considered a benign alternative form of perception most often associated with positive rather than negative outcomes. The condition has been associated with a variety of cognitive and perceptual advantages, including benefits in memory, processing speed, and creativity. It is not currently recognized in the DSM‐IV. Recently, however, several studies have raised the question of a possible link between synaesthesia and clinical conditions. Here, we present the first large‐scale screening of the general population in which we (1) objectively identified grapheme‐colour synaesthetes and (2) elicited information from our participants about a range of clinical conditions. We compared the prevalence rates of these conditions in synaesthetes versus non‐synaesthetes to establish whether any conditions were found at a higher rate among synaesthetes. In our initial study, screening 3,742 people (95 synaesthetes and 3,647 controls), we found initially that grapheme‐colour was significantly comorbid with two conditions (anxiety disorder and obsessive compulsive disorder). In our second study, screening a new population of 120 synaesthetes and 166 non‐synaesthetes, we replicated our finding that grapheme‐colour synaesthesia is comorbid with anxiety disorder. At the same time, we also addressed a methodological concern that likely elevated rates of OCD in Study 1. We consider the aetiology of synaesthesia to determine whether there may be a shared genetic or neurological basis with anxiety disorder, and we question the status of synaesthesia within a mental health framework.