Temporal dynamics of visual and auditory hallucinations in psychosis.

Background: Hallucinations are a core feature of psychosis, often causing considerable distress. Reported prevalence ranges from 70% for auditory hallucinations (AHs) to 30% for visual hallucinations (VHs) and 4% for hallucinations in the tactile domain. AHs have been studied extensively but studies on VHs are scarce. The current study investigated the phenomenology of VHs and AHs in the realm of daily life, by analyzing their prevalence, course and co-occurrence over a 6-day period and their temporal relation to emotions and delusions.

Methods: The ESM, a structured diary technique, was used to investigate hallucinatory experiences in the context of daily life in a pooled data-set of 184 participants (71% males) with psychosis spectrum disorders, which were recruited from mental health facilities in the south of the Netherlands and Belgium. All self-assessments were rated on 7-point Likert scales. VHs were defined using participants' scores on the item "I see phenomena". AHs were measured using the item "I hear voices".

Results: Overall, 73 participants (40%) reported hallucinations. Ten participants reported VHs only, 38 reported both VHs and AHs, and 25 participants reported AHs only. AHs co-occurred with VHs in 40% of the hallucinatory moments. Patients with both VHs and AHs reported higher levels of negative affect, lower levels of positive affect and higher delusional intensity than non-hallucinating patients. Increased delusional intensity preceded the onset of hallucinatory episodes, whereas increases in positive or negative affect did not.

Discussion: These results show that VHs are common in patients with psychosis spectrum disorders and often co-occur with AHs in time. Furthermore delusional ideation may precede hallucinatory episodes in the realm of daily life, rather than result from a hallucination and affective dysregulation might not play a primary role in hallucination onset.