Hearing voices is an experience that is very distressing for many people. Voices – or “auditory verbal hallucinations” – are one of the most common features of schizophrenia and other psychiatric disorders. But for a small minority of people, voice-hearing is a regular part of their lives, an everyday experience that isn’t associated with being unwell. It is only in the past 10 years that we have begun to understand what might be going on in “non-clinical” voice-hearing.
Most of what we know comes from a large study conducted by Iris Sommer and colleagues at UMC Utrecht in the Netherlands. In 2006 they launched a nationwide attempt to find people who had heard voices before but didn’t have any sort of psychiatric diagnosis. From an initial response of over 4,000 people, they eventually identified a sample of 103 who heard voices at least once a month, but didn’t have psychosis. Their voice-hearing was also not caused by misuse of drugs or alcohol.
Twenty-one of the participants were also given an MRI scan. When this group was compared with voice-hearers who did have psychosis, many of the same brain regions were active for both groups while they were experiencing auditory hallucinations, including the inferior frontal gyrus (involved in speech production) and the superior temporal gyrus (linked to speech perception). Subsequent studies with the same non-clinical voice-hearers have also highlighted differences in brain structure and functional connectivity (the synchronisation between different brain areas) compared with people who don’t hear voices.
These results suggest that, on a neural level, the same sort of thing is going on in clinical and non-clinical voice-hearing. We know from first-person reports that the voices themselves can be quite similar, in terms of how loud they are, where they are coming from, and whether they speak in words or sentences.
Knowing that voice-hearing in clinical and non-clinical groups is similar allows us to investigate hallucinations in isolation from other aspects of psychosis, such as having delusional or disorganised thoughts. But it’s just as important to look for the differences between clinical and non-clinical voice-hearing, because it’s the differences that might hold the key to providing better support for those who are unwell or in distress.
There is some evidence that non-clinical voice-hearing tends to start early (around 12 years of age), while voices associated with psychosis usually start in late adolescence and early adulthood. The voices heard in non-clinical groups are also much more likely to be positive and helpful than those experienced by people with psychosis, but it’s not clear why. For many non-clinical voice-hearers, the voice they experience is very important to them. It may provide support and guidance, or have a spiritual aspect.
There is also evidence of subtle cognitive differences between clinical and non-clinical voice-hearers. For example, voice-hearers with psychosis sometimes have difficulty with managing their attention when listening to external sounds. In contrast, a recent study by researchers in Norway suggested that voice-hearers without psychosis don’t appear to have that problem. Voice-hearers with psychosis are also more likely to use an atypical network of brain areas for language, whereas non-clinical voice-hearers seem to show more typical patterns of language functioning.
Knowing more about how voice-hearing develops, especially after being experienced for the first time, is vital to provide better care for those who seek help. Identifying some of the cognitive differences between clinical and non-clinical voice-hearing could also provide clues about the kind of skills you might need to manage voices and make them less disruptive – the protective factors that allow people to hear a voice but carry on with their lives.
Voice-hearing might be a distressing experience for many, but it doesn’t have to be. Another 10 years of research with non-clinical voice-hearers will allow us to understand how and why that’s possible.
This article was originally published here in the Guardian’s ‘Notes and Theories’ science blog on Wednesday 13 August 2014.