Do voice-hearing assessment measures capture the positive experiences of individuals, and to what extent? A systematic review of published assessment measures

ABSTRACT

Background

Many individuals have positive experiences of voice-hearing (VH). However, current assessment tools do not capture positive aspects of VH as comprehensively as they do negative aspects. This may limit assessment and formulation of VH when people seek support from mental health services. Our review question was therefore:- ‘Do voice-hearing assessment measures capture the positive experiences of individuals, and to what extent?’

Method

We conducted a systematic review of assessment measures which included at least one item on VH. We developed a novel framework to define “positive VH experiences”, which was co-produced by clinical experts in psychosis and people with VH experiences. This framework was then used to identify and map items relating to positive aspects of VH.

Results

Thirty-three measures were identified, of which twenty incorporated positive VH experiences. Measures published within the last decade (2009-2019) captured a greater number and diversity of positive VH experiences, compared to measures published prior to 2009. Items relating to the function/intention of voices and the emotional impact, were most commonly identified.

Discussion

Results suggest that research perceptions around VH are broadening and the nuances of experiences are increasingly considered alongside everyday and positive psychological functioning. Implications for both services and voice-hearers are discussed in the paper.

KEYWORDS:

• Review
• auditory hallucinations
• scale
• survey
• tool

Voice-hearing (VH) has been commonly identified in the general population (Johns et al., 2014), and in the past few decades there has been a shift towards considering these experiences as being on a continuum with non-impactful, everyday experiences (Beavan et al., 2011). Despite these changing perceptions, research and interventions still largely adopt the traditional, medicalised view that VH indicates illness and dysfunction (Bentall, 2004), overshadowing both functional and positive VH experiences. In addition, most of the existing literature regarding VH has been conducted with patient groups (i.e. help-seeking individuals), and thus voices are more often viewed as negative and distressing; this may contribute to the perception that many voice-hearers aim to disengage from, suppress or avoid distressing voices (Turkington et al., 2016).

Several studies have demonstrated that beliefs and overall experiences of VH can be positive, much of these emerging from the literature around what has been coined “healthy voice-hearing” (Baumeister et al., 2017; Johns et al., 2014). Positive voice-hearing experiences can include aspects related to the voice itself (i.e. voice content, mannerisms of the voice), the impact the voice has on individuals, and also the way in which voice-hearing affects individuals’ lives and the way they conceptualise these experiences and themselves as voice-hearers. Researchers have shown that the lifetime prevalence of hearing useful and positive voices is around 40–60% in psychotic and non-psychotic populations (Jenner et al., 2008), that 52% of patients report some positive effects of VH (Miller et al., 1993), and around a third of patients experience voices as pleasurable (Sanjuan et al., 2004). A model developed by Beavan et al. (2011) acknowledged the following factors as contributing to positive VH experiences: the voice content is positive, the relationship with the voice is positive and the impact of VH is positive and enriching. Research conducted with participants from non-Western and non-mainstream subcultures (e.g. which value healers, shamans and mediums) has additionally suggested a role for spirituality and religiosity within positive VH experiences. Though the data is sparse, associations have been found between VH experiences and feeling positively connected with higher powers (i.e. gods, spirits, djinns), as well as feeling, or being seen as, gifted or special (Jackson et al., 2011; Ritsher et al., 2004; Stephen & Suryani, 2000). Research has also found cross-cultural differences in the way individuals respond to voices and perceive themselves in relation to their experiences. For example, Luhrmann et al. (2015) found that individuals from the United States experienced voices as volatile and threatening, and also identified with having a psychiatric condition, whereas those from India and Africa experienced voices as harmless and playful and generally were more accepting of these experiences. In this way, it appears that voices are experienced according to an individual’s cultural and societal values, expectations and motivations.

Beliefs that individuals hold about VH can affect whether they engage with services and therefore whether they receive a clinical diagnosis (Johns et al., 2014). One possible reason for non-engagement with services and/or treatment is a concern about losing positive voices or those found to be useful (Jenner et al., 2008). Medication non-compliance within patient groups can also relate to fears of losing the benefits of positively perceived symptoms (Moritz et al., 2013). Mental health professionals can additionally exacerbate these problems by de-emphasising positive VH experiences and focusing on eliminating VH as the overall treatment goal (e.g. Sinha and Ranganathan (2020). This can add to reluctance around seeking help. These are important factors to consider, as individuals who do not engage with services, including those with positive experiences, may have other difficulties that might benefit from intervention (De Leede-smith & Barkus, 2013). To enhance patient engagement and offer tailored treatments, it is necessary for professionals to take a broader, more idiosyncratic stance when providing assessment for people who hear voices. This could lead to more accurate formulations and intervention targets, which honour the helpful aspects of VH that individuals may wish to retain.

In terms of assessment tools, there is a reliance on the use of self-report or interviewer measures to identify and understand VH experiences. Several researchers have looked at the psychometric properties of VH measures and commented on the ongoing development and growing diversity of the aspects captured by such scales. Of note are two systematic reviews which were published 13 years apart; the first by Frederick and Killeen (1998), and a subsequent update by Ratcliff et al. (2011) who explored 10 additional measures. The latter authors observed two patterns within more recently published measures: 1) a significant growth in measures capturing beliefs and interpretations of VH experiences, and 2) a greater number of measures (eight out of ten) which involved self-report. There has not yet been a review of the positive aspects of VH within outcome measures.

The research question for this study was: Do voice-hearing assessment measures capture the positive experiences of individuals, and to what extent?

Method

Our work was conducted in two main stages. Firstly, we conducted a systematic review to identify all published VH measures of psychosis and psychotic-like experiences, including those that have been published in the last 9 years (since the last published review by Ratcliff and colleagues). Secondly, we co-produced a novel framework featuring categories of “positive experiences” of VH by triangulating existing literature with knowledge and views of expert clinicians and experts by experience. This framework was then used to categorise positive experiences of VH captured by included measures.

Stage 1: systematic review of VH measures

Protocol

A detailed review protocol was pre-registered on the Prospero database (https://www.crd.york.ac.uk/PROSPERO; registration number: CRD42019125554) on 15^th February 2019, and the Open Science Framework (https://osf.io/hgjcn/) on 12^th March 2019.

Eligibility criteria

The following inclusion criteria were used

• i) Any measures/tools for assessing VH experiences (Voices specific measures OR any psychosis or psychotic-like experiences measure which includes items about voices).

• ii) Published between December 2009 and January 2019

• iii) Papers from any country, provided they were written in English or an English-language translation is available

Search methods and terms

PUBMED/MEDLINE, PsycInfo and PsycTESTS were searched using terms: voice-hear* (hearers, hearing), auditory hallucinations, instrument, measure, scale, interview (full search terms are provided under Supplementary Materials on the Open Science Framework (OSF), DOI:10.17605/OSF.IO/HGJCN). Reference lists in full text articles and relevant websites (e.g. https://hearingthevoice.org) were hand searched.

Measure selection and data extraction

The titles and abstracts of all records were assessed by the primary reviewer (LA). Full text papers were then independently assessed by the primary (LA) and secondary reviewer (PJ), with “Almost perfect agreement” (Cohen’s k: 0.81) on reasons for exclusion. Where there were disagreements, these were resolved in a joint meeting. The PRISMA flowchart (see Figure 1) outlines the process of identification, screening, eligibility and inclusion for all papers.

Figure 1. PRISMA flowchart of literature search (2009–2019).

Data from the resulting papers were extracted by the primary reviewer, including type of measure, details of service user involvement, and items relating to positive VH.

Stage 2: developing and applying a framework for positive experiences of Voice-Hearing (VH)

The second part of this study was to assess whether published measures of VH captured aspects of positive VH experience. To do this, a framework was co-produced by professionals and experts by experience. This framework consisted of categories of positive VH experience, which drew on evidence from the following sources: a) existing literature on positive experiences of VH, b) mental health websites and forums, c) expert clinical opinions from psychiatry, nursing, social work and psychology representatives, and d) individuals with VH experience including a peer mentor in the NHS and three members of the Hearing Voices Network (HVN).

As these different sources of information were synthesised and triangulated, categories were collapsed, adapted, and refined until five categories remained. Experts with personal experience of VH were integral to this process, and the framework evolved to emphasise subjective aspects of VH experiences as opposed to focusing solely on the content of voices (which may be experienced in many different ways) and objective behaviours of voice-hearers. For example, “impact on life” was reframed as “meaning-making from VH experience” to better capture wider aspects of VH experiences.

Next, the primary reviewer examined and rated items from each of the 33 measures in relation to the framework, and these were recorded in the data extraction form as either being “relevant” or “irrelevant” to each category. Only items that captured positive aspects of VH (rather than negative or neutral aspects e.g. pitch/loudness of voice) were recorded. The secondary reviewer independently reviewed the data extraction forms and rated positive items in the same way using the framework. Ratings were compared and reviewers agreed on the categorisation of 135 out of 151 positive items (89%). Discrepancies were discussed and consensus achieved, leading to a final recategorisation.

Results

Stage one of this project involved providing an update of VH measures for psychosis or psychotic-like experiences that had been published in the last 9 years (since the last review). Thirteen assessment measures met the inclusion criteria. These were broad in their aims, from assessing phenomenological aspects of VH to rating experiences of psychotic symptoms more generally.

Positive experiences of VH framework

Stage two aimed to define what is meant by “positive experiences” of VH and to produce a framework for this, that could then be applied to published measures. Discussions with professionals and experts by experience resulted in the following categories for understanding positive experiences of VH (see Table 1)

Table 1. Framework of positive experiences of voice-hearing

Category	Description
1. Relationship to voice	The relationship between individual and voice is inherently positive, or the voice represents a positive identity for the individual (e.g. protector, guide, companion, kind God/angel).
2. Beliefs/identity about self as voice-hearer	Individual identifies positively with being a “voice-hearer” or believes that hearing voices provides additional possibilities that are positive for them (e.g. being gifted, skilled, sensitivity, balanced).
3. Function/intention of voice	The intention of the voice/s are viewed as positive (e.g. providing reminders, advice, encouragement) or the impact/function that voices have is positive for the individual.
4. Emotional impact of voice	The voice/s lead individuals to feel positive emotionally (e.g. calm, reassured, confident) or they reduce negative affect for the individual.
5. Meaning-making from VH experience	The individual attributes positive overall meaning from the presence of voices/the experience of voice-hearing. This may include how the individual perceives their voice-hearing experiences in relation to their experience of life, well-being, or their connections with others.

Evaluating VH measures using framework of positive experience

Thirty-three measures were evaluated using this framework, including 10 measures from the 1998 review (Frederick & Killeen, 1998), 10 measures from the 2011 review (Ratcliff et al., 2011) and 13 measures first reviewed in this paper. Only measures which listed at least one positive item were included in further descriptions, including seven measures published since 2011. A full list of reviewed measures is provided in the Supplementary Materials on the OSF (DOI:10.17605/OSF.IO/HGJCN).

We found that the majority of measures contained at least one item relating to positive aspects of voice-hearing (20/33; 61%); these are provided in Table 2 alongside the number of scale items within each positive category of VH. For some measures (those marked with *) it was not possible to access exact item wording, despite attempts to contact original authors, therefore data is based on measure descriptions and “sample items”. One item, which asked a two-part question (AHIG; L. N. Trygstad et al., 2015, q.4) was found to relate to more than one category. Service-user involvement was recorded if specifically mentioned as part of scale development; this applied to only three papers.

Table 2. Voice-Hearing (VH) measures with number of scale items relevant to positive experiences categories

Study	Scale	Assessment type	Positive relationship to voice	Positive beliefs/identity about self	Positive function/intention of voice	Positive emotional impact of VH	Positive meaning-making from VH experiences
Lowe (1973)	Phenomenologic characteristics of hallucinations.	Open-ended, unstructured interview			1
Hustig and Ha$fner (1990)	Topography of voices rating scale	Self-report				3
Miller et al. (1993)	RSPH*	Open-ended, Semi-structured interview	2	2	5	1	1
Carter et al. (1995)	MUPS	Semi-structured interview	2		2	1	1
Chadwick and Birchwood (1995)	BAVQ	Self-report	1	1	3	3	2
Oulis et al. (1995)	Clinical characteristics of auditory hallucinations*	Open-ended, semi-structured interview			1
Haddock et al. (1999)	PSYRATS-AH	PSYRATS-AH	1
Birchwood et al. (2000)	VPD	Self-report	6
Chadwick et al. (2000)	BAVQ-R	Self-report	(1)	(1)	(3)	(3)	(2)
L. Trygstad et al. (2002)	CAHQ	Self-report	1			1
Mann and Pakenham (2006)	RAHQ^†	Self-report			2
Shawyer et al. (2007)	VAAS^†	Self-report			1
Hayward et al. (2008)	VAY	Self-report	1		1
Gerlock et al. (2010)	UVS/HCSP	Self-report/clinician protocol				1
Haddock et al. (2011)	SEPS^†	Self-report		2	9	12	8
De Chazeron et al. (2015)	PSAS	Structured interview/Clinician ratings	1
Brockman et al. (2015)	VAAS-12	Self-report			(1)
Perona-Garcelán et al. (2015)	DAIMON^††	Self-report	3		2
L. N. Trygstad et al. (2015)	AHIG	Self-report	1		2
Alderson-Day et al. (2018)	VISQ-R	Self-report	1		2	4
Total items for each category			20	5	31	26	12

*Scale items not available, results are estimations based on measure descriptions or “sample” items. ^†Paper developed with service-users. ^††Paper validated in Spanish, English items provided by authors (English validation study in press). Brackets indicate repeated items in revised measures; these have not been included in category total. Measures: RSPH = Rating scale for phenomenology of hallucinations. SAPS = Scale for Assessment of Positive Symptoms. PANSS = Positive and Negative Syndrome Scale. MUPS = Mental Health Research Institute Unusual Perceptions Schedule. BAVQ/R = Beliefs About Voices Questionnaire/Revised. PSYRATS-AH = Psychotic Symptom Rating Scales-Auditory Hallucinations. VPD = Voice Power Differential. CAHQ = Characteristics of Auditory Hallucinations Questionnaire. AHRS = Auditory Hallucinations Rating Scale. RAHQ = Responses to Auditory Hallucinations Questionnaire. SMVQ = Southampton Mindfulness of Voices Questionnaire. VAAS = Voices Acceptance and Action Scale. HPSVQ = Hamilton Program for Schizophrenia Voices Questionnaire. VAY = Voice and You Scale. UVS/HCSP = Unpleasant Voices Scale & Harm Command Safety Protocol. SEPS = Subjective Experiences of Psychosis Scale. APSS = Adolescent Psychotic-like Symptom Screener. VISQ/R = Varieties of Inner Speech Questionnaire/Revised. PaSI = Panic and Schizophrenia Interview. SSI = Schizotypal Symptoms Inventory. PSAS = Psycho-Sensory hAllucinations Scale. VAAS = Voices Acceptance and Action Scale. AHIG = Auditory Hallucinations Interview Guide. MUSEQ = Multi-modality Unusual Sensory Experiences Questionnaire. CAHSA = Continuum of Auditory Hallucinations-State Assessment.

Measures published in the last decade (2009–2019) incorporated 48 new positive VH items, across seven measures. Measures published during the previous decade (1999–2009) incorporated 14 new positive items across eight measures. Finally, measures published prior to two decades ago (1973–1999) incorporated 33 positive items across seven measures. Measures from the past decade accounted for the highest number of items in the following categories: intention/function of voice, emotional impact of voice, and meaning-making from VH experiences. Measures in the previous decade included the highest number of items in the relationship to voice category. Five items relating to beliefs/identity about self as voice-hearer were captured by measures published in 1993, 1995 and 2011.

Relationship to voices

Twenty items referenced positive relationships with voices or perceptions about the voice/s as holding a positive identity for the voice-hearer. Five items included questions about the companionship or closeness between voice and voice-hearer (e.g. “Does the voice keep you company when you’re lonely?”, Rating scale for phenomenology of hallucinations (RSPH); Miller et al., 1993, q. 5). One measure (DAIMON; Perona-Garcelán et al., 2015), included items that referenced positive ways in which voices spoke about people (e.g. “The voices talk to each other, [saying] nice things about me or the people in my environment”, q. 23) and how voice-hearers in turn communicate positively back to them.

Ten items related to the controllability of VH, with questions relating to feeling strong, powerful and in control of voices. As some items directly linked control and benefit for the voice-hearer (e.g. “The subject believes that he/she can control the voices and make them appear or disappear when he/she wants” (PSAS; De Chazeron et al., 2015, Item 31. Option 1), we decided to include all control related items under this category.

Beliefs/identity about self as voice-hearer

This category was least represented by measures, with five items pertaining to the positive beliefs or interpretations that voice-hearers held about themselves. Two of these items referenced how VH experiences had positively impacted “personality/character” (SEPS; Haddock et al., 2011, q. 8) and “sense of personal identity” (q. 28). Other items referenced whether voices were aiding the individual to develop “special powers or abilities” (BAVQ/R; Chadwick & Birchwood, 1995; Chadwick et al., 2000, q.8/11), and asked how voice-hearers felt about themselves or how others react to them, offering “special” as a suggestion (RSPH; Miller et al., 1993, q.4).

Function/intention of voices

The highest number of positive items (31) was categorised based on perceived intention of the voice and the impact or function of VH for the individual. Included in this category were perceptions of voices as encouraging, helpful, pleasant and friendly (e.g. “In your last illness episode in which you heard the voices, would you say the tone of the predominant voice(s) was generally: (ratings include ‘gentle’, ‘loving’, ‘kind’ and ‘friendly’)?”, (MUPS; Carter et al., 1995, Q. 12). Questions about aspects of performance enhanced by voices or VH included concentration, thought control, memory, socialising, finding work (all SEPS; Haddock et al., 2011, q. 1, 14, 17, 19, 21), ability to work and sexual activity (RSPH; Miller et al., 1993, q.8, 11), and decision-making (VAY; Hayward et al., 2008, q. 2). Six items referenced VH as having a healthy impact on individuals in terms of their sleep, energy, relationships, diet and capacity for self-care (e.g. “in the past week, how have your experiences affected your ability to look after yourself in a positive way” (SEPS; Haddock et al., 2011, q.6). Two items enquired about the protectiveness of the voice (e.g. “My voice wants to protect me”, (BAVQ/R; Chadwick & Birchwood, 1995; Chadwick et al., 2000, q. 4/5).

Emotional impact of voice

Twenty-six items enquired about positive emotional impact of voices and VH. These included feeling calm and reassured (eight items), for example, “During the last 24 hours, how is the tone of your “voices”? (ratings include “moderately comforting” and “very comforting”; (CAHQ; L. Trygstad et al., 2002, q. 5). This category also included inner-speech items, for example, “I calm myself down by talking silently to myself” (VISQ-R; Alderson-Day et al., 2018, q. 27). Five items referenced feelings of happiness, excitement, and “ability to enjoy hobbies and/or activities in a positive way” (SEPS; Haddock et al., 2011, q. 11). Reduction of negative affect was captured in nine additional items (eight of which were in the SEPS), and included positive impact on “levels of anxiety and stress” (q. 4), “feelings of isolation” (q.12), and being able to “easily change topics in my mind and talk to myself about other things” when feeling upset (VISQ-R; Alderson-Day et al., 2018, q. 35).

Meaning-making from VH experience

This category refers to items which capture wider positive beliefs about VH experiences and can be broken down into connection to others and outlook. Eight of these overall items were listed in the SEPS measure (Haddock et al., 2011), which asked about how VH had affected “feelings of discrimination or being judged in a positive way” (q. 25) and “ability to trust others in a positive way” (q.2). Items related to positive outlook referenced future-oriented thinking in relation to voices, for example, “My voice is helping me to achieve my goal in life” (BAVQ/R; Chadwick & Birchwood, 1995; Chadwick et al., 2000, q. 10/14), and how voices had affected “hope for the future in a positive way” (SEPS; Haddock et al., 2011, q. 7).

Three items incorporated positive overall stances on VH, including whether the individual felt “grateful for my voice” (BAVQ/R; Chadwick & Birchwood, 1995; Chadwick et al., 2000, q. 12/17), and how much they “viewed [their] experiences as positive?” (SEPS; Haddock et al., 2011, q. 40).

Discussion

The aim of this systematic review was to identify existing assessment measures for VH, and to define what is meant by “positive VH experiences”. This was to answer the research question: “Do voice-hearing assessment measures capture positive VH experiences, and to what extent?”

This study reviewed 33 measures of VH, including 13 published since 2009, assessing how much these captured positive experiences based on a developed framework. More than two-thirds of measures captured some element/s of positive VH. Findings suggest an increased trend over time for investigating positive aspects of VH, particularly relating to intention/function of voice, emotional impact of voice, and meaning-making from VH experiences. Findings also suggest a growing development of assessment tools capturing hallucinatory experiences in clinical and non-clinical populations.

Trend toward broader “positive” perspectives

The current review highlights a broadening perspective within research and clinical practice: that VH is a subjective and meaningful experience for the individual. The current study found that measures published in the past 10 years (2009–2019) captured a higher number of positive VH items, compared with the preceding decades. This demonstrates an increasing awareness of the complexities of VH perceptions, and perhaps the need for broad, open-ended and/or idiosyncratic assessment tools. It also suggests that capturing positive elements of VH is increasingly viewed as relevant and important when it comes to assessing a person’s whole experience, not just the distressing parts or “symptoms”.

Types of positive experiences captured by measures

Overall, the positive categories most represented by items were intention/function of voice and emotional impact of voice. These categories included items relating to the helpful, entertaining and encouraging nature of voices, along with emotional consequences of VH including feeling comforted and empowered. The importance of “emotional impact” has been previously highlighted as an essential characteristic of VH (Beavan et al., 2011). Previous research has similarly focused on experiences of helpful, pleasant and positive aspects of VH, reported by one third to over 60% of voice-hearers (Jenner et al., 2008; Miller et al., 1993; Sanjuan et al., 2004). Most recently Jenner et al. (2008) found that “protective power” was the biggest reason voices were viewed as positive by VH individuals in both clinical and non-clinical groups.

Relationship to voices was the next biggest category of positive VH, with the highest number of items captured by scales published in 1999–2000. This is unsurprising given the emergence of measures around this time that were designed to focus on beliefs, relationships and power dynamics related to voices (BAVQ; Chadwick & Birchwood, 1995; VAY; Hayward et al., 2008; VPD; Birchwood et al., 2000). This category incorporated several aspects of controllability (i.e. individuals having more control/power than their voices). Controllability has been associated with lower likelihood of complying with command hallucinations (Trower et al., 2004), and a higher likelihood of voices being viewed as pleasurable (Sanjuan et al., 2004). Items in this category also referenced companionship and comfort from voices, which were similarly captured within the “relationships with voices” category of Beavan and colleague’s model of VH (Beavan et al., 2011). Lastly, positive communication and engagement with voices was captured within this category; this has been identified as an important aspect of coping with VH experiences (Andrew et al., 2008).

Positive categories least represented by measures were Beliefs/identity about self as voice-hearer and Meaning-making from VH experience. Regarding the former, there was little to suggest a growing research interest in this area. This lack of specific focus may suggest firstly, that positive beliefs about oneself as a voice-hearer may be captured instead by delusion items within broader measures (e.g. “Do you have special and unusual powers or knowledge/capabilities?” (MUPS Delusions section; Carter et al., 1995, q. 5). Secondly, it is possible that Western-centric outcome measures (and thinking) may result in fewer positive interpretations about the self in relation to VH. Although many other cultures associate VH with spirituality and enlightenment, little of this is conceptualised in mainstream research and practice in the West (McCarthy-Jones et al., 2013). This represents not only a missed opportunity to assess VH beliefs in relation to other cultural understandings, but also limits the reach of practice.

The Meaning-making category incorporates the more powerful and overarching positive impacts of VH, which our experts by experience (those from the HVN) rated most strongly in developing the framework for this review. This category along with “beliefs/identity of self” also incorporated cultural and spiritual perspectives which they related to their own VH experiences. Well-established researchers such as Romme and Escher (1989) have linked individuals’ exploration of voices and their roles with better coping; future measures could benefit from including aspects of meaning related to VH experiences. The SEPS, published in 2011 (Haddock et al.), incorporated most items in this category, suggesting this could be a growing theme within VH research. Interestingly, the SEPS was generated by service-users, demonstrating the importance of involving individuals with personal experience when developing items of value and relevance.

Trend towards VH as being on a continuum with normal experience

This review aimed to align with shifting cultural perceptions surrounding VH, and thus deliberately erred towards inclusivity regarding assessments developed with non-clinical populations and pertaining to “subthreshold” symptoms and “psychotic-like” experiences. For example, the inclusion of measures which investigated “inner speech” (Alderson-Day et al., 2018; McCarthy-Jones & Fernyhough, 2011) was a deliberate decision by reviewers to ensure no false divides were created between internal and externally-located voices. Although less is known about similar measures published prior to 2009 (as will be discussed later), it is interesting that nearly half of the recent measures in this review referenced subclinical auditory hallucinations (i.e. experiences considered to be below the threshold of a clinical “symptom”). It could be hypothesised that this broadening of “symptom” descriptions supports the larger cultural shift towards understanding voice-hearing as common and existing on a spectrum of experience, in line with continuum models of VH (Claridge, 1994; Claridge & Beech, 1995). Some authors also suggest that assessing subclinical experiences increases understanding around predispositions to developing clinical-level symptoms (Kelleher et al., 2011), and for those in recovery, residual experiences and/or risk of relapse (Hodgekins et al., 2012).

Strengths and limitations

In terms of limitations, a number of measures which pertain to voice-hearing or psychotic-like experiences may not have been captured in this review, as they were published prior to December 2009 (and thus outside the parameters of the current search). These were possibly not accounted for in previous reviews for the following reasons. Firstly, search terms across publications may not have been consistent. For example, the Positive and Useful Voices Inquiry (PUVI; Jenner et al., 2008) used the word “inquiry” rather than “instrument”, “scale” or “measure” which were defined in the search terms by Ratcliff et al. (2011). This is unfortunate for the current review as the PUVI directly assesses the characteristics of positive (and useful) voices. Secondly, as the search terms used in the current study were different to those used in the two previous reviews, this has led to the omission of some measures published prior to our dates. Previous reviewers limited their searches to include measures that had only been developed and tested with adult clinical/patient populations. Measures developed with broader participant age ranges, such as the Auditory Vocal Hallucinations Rating Scale (AVHRS; Jenner & Van de Willige, 2002), developed with adults and adolescents, were therefore omitted from the current review.

Related to these acknowledgements we could have taken a more robust approach by conducting broader literature searches with no date limitation, effectively re-reviewing the literature independently. This was beyond the remit for this review, however further research could seek to achieve this. In addition, though the search term “voice-hearing” was felt to be inclusive of a continuum of experiences, it may be that other terms are more commonly used for describing creative, spiritual, and traumatic experiences which may also link to VH. These complexities were considered but were outside the scope of the literature review, and the present authors chose to focus primarily on VH measures for their relevance to clinical assessment. However, exploring the literature around this wider range of experiences could serve to inform future reviews of this kind and to capture measures which may fall outside the established (and Western-centric) HV literature.

A final limitation surrounds the subjective process of assigning scale items to positive framework categories. The complexity of labelling experiences as “positive” and “negative” is acknowledged, though reviewers attempted to conceptualise this from the perspective of voice-hearers, rather than how these experiences may be viewed by others. The same experience can have both positive and negative aspects for individuals. For example, the VAY (Hayward et al., 2008) is described as a measure of “negative relating” to voices, however we considered two items of the dependency subscale as relevant to positive perceptions from the voice-hearer’s perspective, as these may lead individuals to want continued VH experiences. Similarly, items describing how comforting a voice was, could have been categorized under both “intention” and “emotional impact” of VH. Authors considered how individuals may only label a voice as “comforting” if it had a comforting impact on them, thus this was categorised under positive emotional impact. Other researchers may choose to organise and categorise items differently. To be transparent about our methods, a table of categorised items has been provided in the Supplementary Materials on the OSF (DOI:10.17605/OSF.IO/HGJCN).

Clinical implications and future directions

With future research in mind, we suggest that assessment measures are developed to include questions about how VH impacts identity and sense of self, and how individuals make meaning of their experiences. Assessments may be in the form of open-ended interviews or structured self-report measures; a range of methods is possible if there is a balanced inquiry into the nuanced experiences of the individual. Outcome measures for mainstream services should be constructed using a similar approach to that of the SEPS (Haddock et al., 2011), which involved voice-hearers in its development. Professionals should continue to collect feedback about the relevance and acceptability of measures to service-users. In addition, querying self and social identity in relation to voices may further our understanding of voice-hearing from non-Western and non-medical perspectives, bridging the gulf between services and communities. Lastly, a thorough review of VH measures is warranted, to include earlier papers and more nuanced search terms which may not have been captured in previous reviews, particularly those which include sub-clinical VH experiences and non-clinical samples.

Acknowledgements

With thanks to all the professionals and voice-hearers who made this project possible.

Disclosure statement

No potential conflict of interest was reported by the author(s).