In a large study of adults with bipolar disorder, Upthegrove and colleagues report associations between childhood sexual abuse and lifetime occurrence of mood congruent auditory and visual hallucinations; however, no associations are seen for delusions or diagnoses of psychotic disorders. ^{Reference Upthegrove, Chard, Jones, Gordon-Smith, Forty and Jones1} The findings are similar to a recent study of psychotic symptoms in borderline personality disorder (BPD) that shows high lifetime prevalence of auditory and other hallucinations (with predominantly negative contents) but not delusions. ^{Reference Pearse, Dibben, Ziauddeen, Denman and McKenna2} Together these studies provide important clues regarding mechanisms of specific psychopathology. They also raise a wider question regarding the relationships between psychotic and common mental symptoms such as mood and anxiety.

Using interviews with the Present State Examination, the BPD study ^{Reference Pearse, Dibben, Ziauddeen, Denman and McKenna2} found that 80% of 30 patients (collected from a specialist personality disorder service) had experienced psychotic symptoms at some point during their lifetime. Auditory hallucinations were reported by 50% and visual hallucinations were present in about a third of the sample. Although the form of auditory hallucinations was similar to that in schizophrenia, the content was predominantly negative and critical even when they occurred outside an affective episode. Contents of visual and olfactory hallucinations were also mainly negative and unpleasant. Delusions, however, when present, indicated previously undiagnosed psychotic disorder. Although the study did not examine maltreatment specifically, such history is common in BPD. Thus mood dysregulation, which is an important feature of both BPD and bipolar disorder, might explain the emergence of negative, self-critical auditory/visual/other hallucinations in victims of childhood maltreatment.

The findings along with other research indicate psychotic symptoms are common and can occur in the context of non-psychotic disorders. A recent phenomenological study found that auditory hallucinations are present in a diverse sample of people with various diagnoses and clinical histories, where they are associated with fear, anxiety, depression and stress as well as positive or neutral emotions. ^{Reference Woods, Jones, Alderson-Day, Callard and Fernyhough3} In young people, auditory hallucinations have been reported to occur alongside mild to moderate depression and anxiety, where they are a marker of severity, for example multiple psychiatric comorbidity or suicidality. ^{Reference Kelleher, Keeley, Corcoran, Lynch, Fitzpatrick and Devlin4} Similarly, a recent study found that depression, anxiety and psychotic symptoms measure a single, common underlying factor in the population, with psychotic items measuring the more severe end of this continuum. ^{Reference Stochl, Khandaker, Lewis, Perez, Goodyer and Zammit5} Together these findings suggest that similar to depression and anxiety, psychotic symptoms – particularly auditory hallucinations – are common mental symptoms. Therefore, psychotic phenomena should be routinely included in epidemiological assessments of psychiatric morbidity. Diagnostic classification systems should acknowledge the presence of psychotic symptoms in non-psychotic disorders to reflect evidence, which will also allay worries among patients and many clinicians who tend to associate hallucinations exclusively with psychosis.