Koro: a socially-transmitted delusional belief

ABSTRACT

Introduction

Koro is a delusion whereby a man believes his penis is shrinking into his abdomen and this may result in his death. This socially-transmitted non-neuropsychological delusional belief occurs (in epidemic form) in South-East and South Asia. We investigated whether the two-factor theory of delusion could be applied to epidemic Koro.

Methods

We scrutinised the literature on epidemic Koro to isolate features relevant to the two questions that must be answered to provide a two-factor account: What could initially prompt the Koro delusional hypothesis? Why is this hypothesis adopted as a belief?

Results

We concluded that the Koro hypothesis is usually prompted by the surprising observation of actual penis shrinkage—but only if the man has access to background beliefs about Koro. Whether the hypothesis is then adopted as a belief will depend on individual factors such as prior belief in the Koro concept or limited formal education and sociocultural factors such as deference to culture, to media, or to rumours spread by word of mouth. Social transmission can influence how the first factor works and how the second factor works.

Conclusion

The two-factor theory of delusion can be applied to a socially-transmitted delusion that occurs in epidemic form.

KEYWORDS:

• Koro
• suo-yang
• delusion
• two-factor theory of delusion
• hypothesis generation

Acknowledgements

We are grateful to the editor and two anonymous reviewers for their constructive comments on an earlier version of this paper.

Data availability statement

There is no data set associated with this article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 Our account of these events in Fuhu village is drawn from Li (2010).

2 In many of the Koro epidemics we discuss in this paper, including the 1984/85 Hainan/Leizhou epidemic, there were some female cases. These involved the beliefs that the nipples were retracting into the body and/or the labia were shrinking. Male cases always predominated and no detailed reports of individual female cases exist. For these reasons we do not discuss female cases in our paper.

3 Most case descriptions have been paraphrased and abbreviated.

4 According to Ng and Kua (1996, p. 563) “The term ‘koro' is thought to derive from the Malay word ‘kura' which means ‘tortoise’ – the symbolic meaning is that the penile retraction is compared with the retraction of the head of the tortoise into its shell.”

5 A reviewer suggested that the Koro belief is not a delusion because it is not maintained in the face of contrary evidence.

6 We are not the first to draw attention to this evidence. Mo et al. (1995, p. 243) commented on the “challenging question” why people hold background cultural beliefs about Koro and, specifically, adopt and maintain the Koro belief in Koro epidemics, despite the evidence that “no person has actually died from a koro attack”.

7 We do not find a Glossary in the 2022 text revision of DSM-5 (DSM-5-TR, American Psychiatric Association, 2022).

8 A Sanskrit text on Ayurveda traditional medicine dating back more than two millennia.

9 What we say here is intended to apply whether one hears about a case by word of mouth, or hears about it on the telephone or on the radio, or reads about it in a newspaper, or via television.

10 A reviewer asked why, given that the cultural background beliefs about Koro are a stable feature of the community, there are sudden exponential increases in adoption of the Koro delusional belief. In the case of the outbreak of Koro at the Fuhu village school in May 2004, the answer seems clear. Against the stable background of “people’s common knowledge of suoyang” (Li, 2010, p. 104), the unique outbreak was triggered by the principal's address warning the children to be cautious about Koro and to take emergency measures if they experienced symptoms.

11 When young children are involved in a Koro epidemic, there may be an element of folie à deux or folie imposée (see Langdon, 2013, for application of the two-factor theory of delusion to folie à deux).

Additional information

Funding

The authors reported there is no funding associated with the work featured in this article.