Symptoms that are linked to schizophrenia and other psychotic disorders, such as auditory verbal hallucinations (AVH), are also commonly reported by individuals who function well in society. These individuals are not in need for care, do not suffer from schizotypal personality disorder or other psychotic disorders, and provide the opportunity to investigate the relationship between nonclinical psychotic symptoms and brain morphology.

Fifty individuals with nonclinical AVH, 50 patients with a psychotic disorder and AVH, and 50 healthy controls underwent structural magnetic resonance imaging. The three groups were matched for age, gender, handedness and years of parental education. Cortical thickness was assessed using the FreeSurfer software suite.

Cortical thickness in the left pars orbitalis, left paracentral gyrus, right fusiform gyrus and right inferior temporal gyrus was lowest in patients, intermediate in the nonclinical AVH group, and highest in controls. The patients also showed additional cortical thinning in widespread frontal, temporal and parietal areas compared to both other groups. In additional analysis, ranking the levels of cortical thickness per brain region across groups revealed that for the large majority of brain regions (88%), the patients had the lowest cortical thickness, the nonclinical individuals with AVH were in between, and the control subjects had the highest cortical thickness.

Individuals with nonclinical psychotic symptoms show a similar but less pronounced pattern of cortical thinning as patients with a psychotic disorder, which is suggestive of a similar, but milder underlying pathophysiology in the nonclinical hallucinating group compared to the psychosis group.

Previously, we described 103 adults (mean age 41 years) who experienced frequent, auditory verbal hallucinations (AVH), in the absence of a need for mental healthcare. Importantly, these adults were largely past the peak incidence age for psychosis (15–35 years). It is unclear if these older individuals with AVH are still at increased risk for psychosis or other psychopathology. To address this question, we conducted a 5-year follow-up of previously included individuals (103 with AVH, 60 controls).

Eighty-one adults with AVH (78.6%) and forty-nine controls (81.7%) could be contacted and were willing to participate. Participants were screened for psychosis and a need for mental healthcare at follow-up using the Comprehensive Assessment of Symptoms and History interview (CASH). Need for mental healthcare was defined as a clinical diagnosis as identified using the CASH and/or treatment by a mental healthcare specialist. Phenomenology of AVH was assessed with the PSYRATS Auditory Hallucinations Rating Scale.

Five individuals with AVH (6.2%) had developed psychosis and 32 (39.5%) had developed a need for mental healthcare. Voice-related distress at baseline significantly predicted need for mental healthcare. AVH persisted in most individuals (86.4%), without significant changes in phenomenology. None of the controls had developed psychotic symptoms, and need for mental healthcare (n = 6, 12.2%) was significantly lower in this group.

These findings suggest that frequent AVH in non-psychotic adults past the peak incidence age for psychosis constitute a rather static symptom and that individuals with AVH may be best viewed as situated on a need for care continuum.

Several cognitive biases are related to psychotic symptoms, including auditory verbal hallucinations (AVH). It remains unclear whether these biases differ in voice-hearers with and without a ‘need-for-care’.

A total of 72 healthy controls, 72 healthy voice-hearers and 72 clinical voice-hearers were compared on the Cognitive Biases Questionnaire for psychosis (CBQp), which assesses ‘intentionalizing’, ‘jumping to conclusions’, ‘catastrophizing’, ‘dichotomous thinking’ and ‘emotional reasoning’ in vignettes characterized by two themes, ‘threatening events’ and ‘anomalous perceptions’.

Healthy voice-hearers scored intermediately on total CBQp between the control and clinical groups, differing significantly from both. However, on four out of five biases the scores of the healthy voice-hearers were comparable with those of the healthy controls. The only exception was ‘emotional reasoning’, on which their scores were comparable with the clinical group. Healthy voice-hearers demonstrated fewer biases than the psychotic patients on the ‘threatening events’, but not the ‘anomalous perceptions’, vignettes. CBQp scores were related to both cognitive and emotional, but not physical, characteristics of voices.

Most cognitive biases prevalent in clinical voice-hearers, particularly with threatening events themes, are absent in healthy voice-hearers, apart from emotional reasoning which may be specifically related to the vulnerability to develop AVH. The association between biases and both beliefs about voices and distress/emotional valence is consistent with the close links between emotions and psychotic phenomena identified by cognitive models of psychosis. The absence of reasoning biases might prevent the formation of threatening appraisals about anomalous experiences, thereby reducing the likelihood of distress and ‘need for care’.

Although auditory verbal hallucinations (AVH) are a core symptom of schizophrenia, they also occur in non-psychotic individuals, in the absence of other psychotic, affective, cognitive and negative symptoms. AVH have been hypothesized to result from deviant integration of inferior frontal, parahippocampal and superior temporal brain areas. However, a direct link between dysfunctional connectivity and AVH has not yet been established. To determine whether hallucinations are indeed related to aberrant connectivity, AVH should be studied in isolation, for example in non-psychotic individuals with AVH.

Resting-state connectivity was investigated in 25 non-psychotic subjects with AVH and 25 matched control subjects using seed regression analysis with the (1) left and (2) right inferior frontal, (3) left and (4) right superior temporal and (5) left parahippocampal areas as the seed regions. To correct for cardiorespiratory (CR) pulsatility rhythms in the functional magnetic resonance imaging (fMRI) data, heartbeat and respiration were monitored during scanning and the fMRI data were corrected for these rhythms using the image-based method for retrospective correction of physiological motion effects RETROICOR.

In comparison with the control group, non-psychotic individuals with AVH showed increased connectivity between the left and the right superior temporal regions and also between the left parahippocampal region and the left inferior frontal gyrus. Moreover, this group did not show a negative correlation between the left superior temporal region and the right inferior frontal region, as was observed in the healthy control group.

Aberrant connectivity of frontal, parahippocampal and superior temporal brain areas can be specifically related to the predisposition to hallucinate in the auditory domain.

Hallucinations have consistently been associated with traumatic experiences during childhood. This association appears strongest between physical and sexual abuse and auditory verbal hallucinations (AVH). It remains unclear whether traumatic experiences mainly colour the content of AVH or whether childhood trauma triggers the vulnerability to experience hallucinations in general. In order to investigate the association between hallucinations, childhood trauma and the emotional content of hallucinations, experienced trauma and phenomenology of AVH were investigated in non-psychotic individuals and in patients with a psychotic disorder who hear voices.

A total of 127 non-psychotic individuals with frequent AVH, 124 healthy controls and 100 psychotic patients with AVH were assessed for childhood trauma. Prevalence of childhood trauma was compared between groups and the relation between characteristics of voices, especially emotional valence of content, and childhood trauma was investigated.

Both non-psychotic individuals with AVH and patients with a psychotic disorder and AVH experienced more sexual and emotional abuse compared with the healthy controls. No difference in the prevalence of traumatic experiences could be observed between the two groups experiencing AVH. In addition, no type of childhood trauma could distinguish between positive or negative emotional valence of the voices and associated distress. No correlations were found between sexual abuse and emotional abuse and other AVH characteristics.

These results suggest that sexual and emotional trauma during childhood render a person more vulnerable to experience AVH in general, which can be either positive voices without associated distress or negative voices as part of a psychotic disorder.

Auditory verbal hallucinations (AVH) in patients with borderline personality disorder (BPD) are frequently claimed to be brief, less severe and qualitatively different from those in schizophrenia, hence the term ‘pseudohallucinations’. AVH in BPD may be more similar to those experienced by healthy individuals, who experience AVH in a lower frequency and with a more positive content than AVH in schizophrenia. In this study the phenomenology of AVH in BPD patients was compared to that in schizophrenia and to AVH experienced by non-patients.

In a cross-sectional setting, the phenomenological characteristics of AVH in 38 BPD patients were compared to those in 51 patients with schizophrenia/schizoaffective disorder and to AVH of 66 non-patients, using the Psychotic Symptom Rating Scales (PSYRATS).

BPD patients experienced AVH for a mean duration of 18 years, with a mean frequency of at least daily lasting several minutes or more. The ensuing distress was high. No differences in the phenomenological characteristics of AVH were revealed among patients diagnosed with BPD and those with schizophrenia/schizoaffective disorder, except for ‘disruption of life’, which was higher in the latter group. Compared to non-patients experiencing AVH, BPD patients had higher scores on almost all items.

AVH in BPD patients are phenomenologically similar to those in schizophrenia, and different from those in healthy individuals. As AVH in patients with BPD fulfil the criteria of hallucinations proper, we prefer the term AVH over ‘pseudohallucinations’, so as to prevent trivialization and to promote adequate diagnosis and treatment.