Roughly 1 in 30 people will experience at least one psychotic episode in their lives. While the conversation about such hallucinations typically focuses on the auditory and visual, many who live with psychosis know how limited this perspective can be.

Now researchers have turned their attention to the rich palette of experiences that accompany hallucinatory episodes, developing a body-map depicting the kinds of emotion, awareness, and even tactile sensation that often complicates a diverse range of neurological disorders.

Psychologists from the University of Leicester in the UK recruited a dozen volunteers through the National Health Service's Early Intervention in Psychosis teams, and asked them to document the hallucinations that occurred in everyday life for a week.

The diary was structured in a way that the participants could also keep note of any other emotions, sensations, or even cognitive states that coincided with the visual and auditory symptoms considered more typical of psychosis.

At the end of the seven days, the volunteers had a half-hour long face-to-face interview with one of the researchers, where the two went through the diary in detail and discussed its records.

The result was a kind of map that broke down the boundaries of hallucinations, describing them as events that can affect just about any part of the body.

"The range of feelings in the body and around the body (into peri-personal space) were particularly interesting," says study lead author, Katie Melvin.

"Participants often described that the method helped them share experiences that were difficult to put into words."

Hallucinations have long been a hallmark of mental illness, in spite of being a common experience many of us have. Hearing a voice that never called, or seeing things from the corner of our eye isn't always indicative of some kind of pathology.

For those living with conditions such as schizophrenia, advanced Alzheimer's, or psychotic depression, constantly trying to separate phantoms woven by the mind from reality can be exhausting, confusing, and – for some – downright terrifying.

What's more, personal experiences can vary considerably, impacting on quality of sleep, motivation, and ability to interact with others or even hold down a job.

While it's been clear that hallucinations can be diverse, until now nobody has attempted to quantify the range of feelings that can arise.

Though it's a small sample, the 12 people involved in this study are just a starting point, giving us a basis for asking the question of just how common 'multimodal unusual sensory experience' – or MUSE – might be.

"MUSE maps involve documenting hallucinations in daily life and include body-mapping. The article shares new insights through body-maps and data on the immediate feeling of hallucinations," says Melvin.

Among those who hear voices, for example, the volume alone can vary considerably. Up to a third of the participants heard them as whispers, for example. Around a quarter experienced them as shouts or screams.

Nearly half had a churning stomach, or butterflies, prior to or when hearing voices. There were also mentions of more intense sensations, of being held down, of nausea, or in some cases physical pain. Reports included descriptions of tingling sensations in the limbs, and one's body feeling as if it was on fire.

"There's something on my tongue," reports one of the participants. Another describes a sense of "something in the way of my vagina."

Beyond sensations, there were also altered states of cognition. At one extreme, it might simply be an extreme sense of boredom. At the other, a hyper-aroused state of alertness, or overthinking.

Feelings that inferred some state of reality were reported by nearly all of the participants, of being watched by something malevolent, feeling disconnected, or simply the overwhelming nature of the entire experience.

Specifics aside, it's clear that by focusing on hallucinations as things that are just seen or heard, we're missing out on a bigger picture. In this sample alone, 83 percent of the participants experienced a broad range of emotions, sensations, and feelings in their psychosis.

Learning how these maps represent the population at large could help point the way to better therapies that help individuals find ways to cope with the challenges that come with their particular mix of experiences.

"The next steps for this area of research will be further understanding the embodiment and feeling of hallucinations in different populations and developing interventions to support with this," says Melvin.

This research was published in EClinicalMedicine.