Increases in Autonomic Function May Predict Auditory Hallucinations in SCZ

Increases in autonomic function may predict the occurrence and severity of auditory hallucinations in patients with schizophrenia, suggesting a regulation of these experiences by the autonomic nervous system. The study, conducted by an international group of researchers from the United States, The Netherlands, and the United Kingdom, was recently published in Schizophrenia Bulletin.¹

Approximately 70% of individuals with schizophrenia experience auditory hallucinations, which describe the phenomenon of “hearing a voice with a compelling sense of reality in the absence of an appropriate external stimulus.”² Since 2012, biennial meetings of the International Consortium on Hallucinations Research have been held as a means to “provide a scientific platform for researchers, mental health professionals, and people with a lived experience of ‘voices’ and other hallucinations to collaborate on research topics related to hallucinations, and to act as a vehicle for the cross-fertilization of ideas,” highlighting the increase in interest in the field. The fourth such meeting will take place in November 2017 in Lille, France.

Despite this trend, the mechanisms underlying auditory hallucinations are still poorly understood. A model that was proposed — that of “inner speech” or verbal self-monitoring — posits that auditory hallucinations “result from self-monitoring deficits leading to inner speech not being recognized as self-produced, and instead being perceived as an autonomous, non-self voice.”³ The second predominant model for auditory hallucinations is based on intrusions of memories or “unintentional activation of memories,” or, still, a “failure to inhibit irrelevant memories.”⁴

Both the frequency (from nearly continual to sporadic) and duration (lasting a few seconds to several hours) of auditory hallucinations are highly variable across and within individuals.⁵ Negative emotions (eg, stress) may act as triggers and promoting factors for auditory hallucinations (and other psychotic symptoms), thus explaining the “ebb-and-flow” characteristic of this phenomenon. This association is supported by patients with schizophrenia reporting anxiety as the dominant emotion preceding and co-occurring with auditory hallucinations, “suggesting that negative emotions are a cause, rather than a consequence of AH.”^1,6

As emotions (negative and positive) are associated with physiological responses that are regulated by the autonomic nervous system, researchers have hypothesized that this system may be implicated in auditory hallucinations — be it in their onset, exacerbation, amplification, and/or modulation.

In the current study, researchers used the experience sampling method (ESM), “an ecologically valid, time sampling of self-reports developed to study the dynamic process of person-environment interactions,” which allows “assessment of real-world, real-time experiences (ie, in situ and in vivo) with limited need of episodic memory input and minimal impact of cognitive biases.” The ESM relies on the use of electronic mobile devices (iESP software ver. 3.3; Intel Research Center) to precisely time autonomic responses and auditory hallucinations of study participants.

A total of 40 participants (average age, 30.5; 62% men; average severity of auditory hallucinations, 3.08 on the 1 to 100 Scale for Assessment of Positive Symptoms) diagnosed with schizophrenia (using Diagnostic and Statistical Manual of Mental Disorders-IV criteria), and experiencing moderate to severe non-affective psychoses, were included in the study. Study participants were assessed over a 36-hour period, during which they were asked — when prompted by beeps randomly scheduled during daytime hours for a total of 10 prompts — to assess the severity of their auditory hallucinations, by answering a brief questionnaire presented on the mobile device. The questionnaire also covered an evaluation of the study participants’ mood, activities, and social context. Upon completion of the ambulatory study period, auditory hallucinations were evaluated using the Psychotic Symptom Rating Scale.

Autonomic regulation of cardiac and pulmonary functions was concurrently assessed by measuring “cardiac vagal contribution to heart rate variability,” using an undershirt garment (LifeShirt System, VivoMetrics) embedded with sensors consisting of electroencephalogram electrodes.

Study participants responded to 89.8% of the ESM prompts (average of 17.8 responses). Auditory hallucinations were experienced in 40% of the sample and had an average severity of 30.68 (SD, 34.80), with 61% reported as severe.

A significant negative association was found between auditory hallucinations and vagal input over the 5 minutes preceding the prompt during the ambulatory study period, using a mixed-effect regression model (b=−1.44; SE = 0.73; P =.049; effect size, −0.08). In addition, a negative correlation was found between auditory hallucinations and vagal input (r = −0.36; P =.03).

This study indicates a temporal association between auditory hallucinations and autonomic function. “Our results provide preliminary support for a model in which increases in autonomic arousal contribute to onset and/or exacerbation of [auditory hallucinations]…and suggest autonomic arousal precedes and may trigger the onset and exacerbation of [auditory hallucinations],” concluded the investigators.

Limitations

• Small number of participants (n=40)
• Short assessment period (36 h)
• Assessment of auditory hallucinations using a single question

Reference

Kimhy D, Wall MM, Hansen MC, et al. Autonomic regulation and auditory hallucinations in individuals with schizophrenia: an experience sampling study [published online February 8, 2017]. Schizophr Bull. doi:10.1093/schbul/sbw219