Background: Delusions involving the internet have been reported as examples of the influence of cultural innovations on delusion formation, although there has been some debate as to whether such innovations simply affect surface content, or whether they have more substantial clinical or psychopathological implications. Sampling and Methods: Four cases of patients with delusions involving the internet were identified following a general request to local consultant psychiatrists for referrals. Results: The internet had a specific effect on aetiology in one case, and knowledge of the internet seemed to constrain the type of delusion formed in two others. The presence of an internet-related delusion in the final case was used to frame a successful clinical intervention based on the ‘collaborative empiricism’ method, using cognitive behavioural therapy and collaborative use of the internet to resolve the delusional belief. Conclusions: Cultural technical innovations may have specific influences on the form, origin and content of delusional beliefs. For some patients the presence of internet-themed delusions may be a good prognostic indicator since, given the rich sources of information available, they may be well suited to treatment with cognitive behavioural therapy.

Background: The DSM criteria for a delusion indicate that it should not include any beliefs held by a person’s ‘culture or subculture’. The internet has many examples of people reporting ‘mind control experiences’ (MCEs) on self-published web pages, many of which suggest a community based around such beliefs and experiences. It was hypothesized that some of these reports are likely to reflect delusional beliefs and the hyperlinks between web reports were likely to show evidence of social structure, demonstrating the ‘culture or subculture’ exemption to be increasingly redundant in light of new technology. Sampling and Methods: Texts from web sites reporting MCEs (n = 10), experience of cancer (n = 10), depression (n = 10) and being stalked (n = 10) were identified, and were blind-rated by three independent psychiatrists for the presence of delusions. Hyperlinks from web sites reporting MCEs were used to create a network structure; this was compared with a size-matched, randomly generated network and known social networks from the literature using social network analysis. Conclusions: The sampled web-published accounts of MCEs are highly likely to be influenced by delusional beliefs. Social network analysis suggests there is significant evidence of an online community based around these beliefs. The fact that individuals can form a community based on the content of a potentially delusional belief presents a paradox for the DSM diagnostic criteria for a delusion, and suggests the need to revise and revisit the original operational definition in the light of these new technological developments.