Neuropsychiatric Manifestations in Breath‐Hold Divers and the Folklore of <i>Tomokazuki</i>

ABSTRACT Diving can affect neuropsychiatric functions. Previous studies of Taravana syndrome in Polynesian pearl divers, which have similarities to decompression illness following breath‐hold diving, and of Chiyamai in Japanese breath‐hold divers, which have symptoms like panic disorder, show what modern medicine can learn from the wisdom of tradition. Among Japanese traditional breath‐hold divers, known as Ama , in the Shima region, there is frightening folklore about something called Tomokazuki , a phantom‐like figure that appears to an Ama in life‐threatening situations. Although Tomokazuki may be a medically explainable phenomenon, to date it has not been analyzed scientifically. We review neuropsychiatric manifestations in traditional breath‐hold divers, with a particular focus on Iwata Junichi's Ama of Shima , published in 1939, which records the traditional fishing practices of the Ama and includes 12 orally passed down episodes concerning Tomokazuki. Seven of the 12 Tomokazuki episodes were self‐like visions, four were visions of others, and the remaining one was an auditory experience of a voice. Three episodes described feelings of being separated by a netlike membrane (similar to mosquito netting). Hypothermia, loss of consciousness due to hypoxia, sensory deprivation, isolation, and exhaustion were presumed to relate to the hallucinatory events both individually and in combination. The contents of hallucinations in similar occupational, sport, and clinical situations have not been well researched. Tomokazuki deserves attention from sociological and medical perspectives.