Why Do Some People With Schizophrenia Hear Voices That Aren’t There?

People diagnosed with schizophrenia experience a wide range of symptoms, with a significant percentage reporting visual and auditory hallucinations, meaning they may hear voices and other noises that aren’t there, and/or see people and objects that aren’t there.

That’s one reason mental health disorders like schizophrenia often scare and/or confuse people who don’t know anything about them or have never met a person with schizophrenia. The symptoms often lead to. behavior that others label as bizarre or unusual. However, mental health professionals avoid words like that, because they imply a level of normative judgment that can lead to stigma and discrimination.

Instead, it’s common to refer to behavior associated with schizophrenia as atypical, since the word implies no judgment: typical behavior is what most people engage in, while atypical behavior is behavior a small percentage of people engage in.

When we’re talking about schizophrenia, we’re talking about a small percentage of the overall population. The National Institute of Mental Health (NIMH) and the study “An Evaluation Of Variation In Published Estimates Of Schizophrenia Prevalence From 1990─2013: A Systematic Literature Review” show the following:

• 12-month, past year diagnosis of schizophrenia: 0.33%
  • Among adults in the U.S., that’s about 850,000 people
• Ever-diagnosed, lifetime incidence of schizophrenia: 0.48%
  • Among adults in the U.S., that’s about 1.25 million people

Although we understand how to support people with schizophrenia and help them reduce and/or manage their symptoms to decrease the amount of disruption they cause in daily life, we still don’t understand what causes schizophrenia, nor do we understand the mechanisms in the brain that cause hallucinations – until now.

New Research on Auditory Hallucinations Associated With Schizophrenia

The study “Impaired Motor-To-Sensory Transformation Mediates Auditory Hallucinations” explores the underlying brain processes that may cause auditory hallucinations in people with schizophrenia. but we may need to offer assistance in understanding the way they discuss their research. Here’s how they introduce their study:

“We hypothesize that selective impairments in functionally distinct signals…during motor-to-sensory transformation cause the positive symptoms of hallucinations.”

Translation: problems in sending signals from one area of the brain to another immediately before speaking cause auditory hallucinations. Before, during, and after we speak, our brain is hard at work, even if we don’t realize it. When we’re about to talk – a motor skill – part of our brain turns off our ability to hear the sound of our own voice inside our head – a sensory skill. In the hypothesis above, the researchers propose that disruptions in those signals create auditory hallucinations – the voices in their head – that some people with schizophrenia experience.

Were they right?

We’ll share the results in a moment. First, we’ll offer a definition of schizophrenia and briefly discuss the symptoms of schizophrenia.

What is Schizophrenia? Overview and Symptoms

Here’s an evidence-based definition of schizophrenia published by the Merck Manuals, based on criteria identified in the Diagnostic and Statistical Manual of Mental Disorders, Volume 5 Text Revision (DSM-V TR):

“Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking and behavior, reduced expression of emotions, diminished motivation, a decline in mental function (cognition), and problems in daily functioning, including work, social relationships, and self-care.”

Experts indicate the symptoms of schizophrenia appear in four forms – positive, negative, disorganized, and cognitive – which may vary from one patient to the next:

• Positive symptoms include hallucinations and delusions.
• Negative symptoms include the loss of typical emotional or social functioning.
• Disorganized symptoms include rambling or incoherent speech, revealing disorganized thoughts and patterns of thought, and also include atypical, inappropriate behavior driven by disorganized or atypical patterns of thought.
• Cognitive symptoms include difficulty with memory, impaired information processing, and impaired problem-solving ability

Not all patients experience all the symptoms of schizophrenia, but all patients diagnosed with schizophrenia experience at least one symptom from all four categories. These symptoms can cause severe disruption across all areas of life, and have a negative impact on relationships, family life, school achievement, and vocational ability.

However, patients with schizophrenia can and do learn how to manage their symptoms and live full and productive lives. That’s why research like the study we discuss in this article is vital: the better we can understand the physical cause, i.e. the brain mechanism responsible for auditory hallucinations, the better we can help patients with schizophrenia.

The Results: Does a Problem With Brain Signaling Cause Auditory Hallucinations, i.e. Cause People With Schizophrenia to Hear Voices?

The research team asserts their experimental results confirm their hypothesis, which means that yes, for the first time, we have an understanding of why some people with schizophrenia hear voices that aren’t there.

Here’s what they found:

1. In a person without schizophrenia, speech works like this:
   1. Intention to speak appears in brain
   2. Brain sends signals to prepare, including a corollary discharge (CD) and an efference copy (EC).
   3. Speech occurs.
2. In a person with schizophrenia but without auditory hallucination, the speech process changes slightly:
   1. Intention to speak appears in brain
   2. Brain sends signals to prepare, but the corollary discharge (CD) is relatively weak/disrupted.
   3. Speech occurs.
3. In a person with schizophrenia with auditory hallucinations, the internal speech process is disrupted:
   1. Intention to speak appears in brain.
   2. Brain sends signals to prepare, but the corollary discharge (CD) is weak to nonexistent and the efference copy (EC) is significantly amplified.
   3. Speech occurs.

However, when speech occurs in example #3, the individual cannot distinguish between internal thoughts and external sensory input. This means that a person may hear the thoughts inside their own head the same way they hear sounds coming from an external source.

In other words, disruptions in brain signaling make it impossible to distinguish external sounds from internally generated thoughts, resulting in what we call, and some people with schizophrenia experience as hallucinations.

The changes – i.e. the extremely weak CD and amplified EC – appeared only in patients with schizophrenia who report auditory hallucinations. This is a major finding: when we can identify a specific process connected to a specific phenomenon, we can then work to remediate that process and restore optimal function.

This means that in the future, when scientists follow though on this research, we may be able to find a way to reduce or completely eliminate auditory hallucinations, which would be a significant step forward in the treatment of schizophrenia.