The frequency of shared delusions in delusions of infestation

Eur Arch Psychiatry Neurol Sci. 1990;239(4):263-6. doi: 10.1007/BF01738581.


The phenomenon of shared delusions was found in 9 (8.4%) of 107 personally investigated patients suffering from delusions of infestation (88 females, 19 males). A greater number of females (ratio of females to males 3.5:1) "induced" others, whereas a gender ratio of 1:1 was evident in the group of affected patients. Since the ratio of blood relations to non-blood relations was 1:2.3, genetic factors seem to play a less important role than the direct impact of deluded patients on their environment. The rare occurrence of shared delusions of infestation leads to the conclusion that only persons with a paranoid predisposition (paranoide Bereitschaft) may be affected. Cases of induced delusions are also described in which attending physicians act as "inducers".

MeSH terms

  • Austria / epidemiology
  • Cross-Sectional Studies
  • Delusions / epidemiology*
  • Delusions / genetics
  • Delusions / psychology
  • Ectoparasitic Infestations / epidemiology*
  • Ectoparasitic Infestations / psychology
  • Female
  • Humans
  • Incidence
  • Male
  • Risk Factors
  • Sex Factors
  • Shared Paranoid Disorder / epidemiology*
  • Shared Paranoid Disorder / genetics
  • Shared Paranoid Disorder / psychology