Freeman et al have used an innovative technique in a non-clinical population to confirm a high background prevalence of negative, mistrustful and fearful thoughts about others. ^{Reference Freeman, Pugh, Antley, Slater, Bebbington, Gittins, Dunn, Kuipers, Fowler and Garety1} Their paper may be helpful in encouraging healthcare professionals in their attempts to normalise rather than medicalise such thoughts, which are particularly common and pronounced in patients with neurotic and personality disorders. ^{Reference Reid and Thorne2}

I am concerned, however, by the authors' use of the word ‘paranoia’ to describe these thoughts. Freeman et al define paranoia as ‘the unfounded fear that others intend to cause you harm’, with reference only to an earlier publication by the main author; later in the paper the words ‘persecutory’ and ‘paranoid’ are used synonymously. This definition and usage are erroneous.

Varying definitions of paranoia exist in the literature but the correct meaning of ‘paranoid’ is ‘delusional’. ^{Reference Hamilton3} With a Greek derivation and a literal meaning of ‘out of the mind’, German psychiatrists revived the term in the mid-19th century to describe conditions characterised by delusions, not only of persecution but also of grandeur. ^{Reference Gelder, Gath, Mayou and Cowen4} Later, Kraepelin, Bleuler and others variously attempted to classify paranoia, but central to all concepts was that it referred only to delusional rather than non-delusional ideation, and could include grandiose, jealous or somatic, as well as persecutory, delusions. ^{Reference Gelder, Gath, Mayou and Cowen4} Indeed, the ‘paranoid’ subtype of schizophrenia, still in use, refers to an illness dominated by hallucinations and delusions, and the latter need not be persecutory in nature. ⁵

Of course, over the 20th century, the word has taken on an entirely different meaning outside psychiatry. Anecdotally, patients frequently report ‘paranoia’ as an unpleasant presenting complaint, despite the fact that, by its very nature, a fixed false belief cannot be viewed by its sufferer as a symptom. Similarly, mental health professionals commonly use the term erroneously, sometimes resulting in non-psychotic patients being inappropriately referred to specialist services for those with psychosis. I fear that Freeman et al's rejection of the longstanding psychiatric definition of paranoia, in favour of its lay meaning, will only add to this unnecessary confusion.