Introduction

Insight in psychosis, broadly defined as a patient’s awareness and judgment of their mental illness, has been a contentious and evolving concept throughout psychiatric history. Before the mid-19th century, the absence of insight was often considered a defining characteristic of psychosis. The concept of insight in psychosis seemed contradictory, as insanity was primarily understood as the manifestation of delusional cognition. However, the emergence of concepts like self, consciousness, and introspection in the mid-19th century, along with the inclusion of subjective experiences in the definition of insanity, gradually paved the way for comprehending the possibility of individuals recognizing their mental illness [1].

Scholars have since attempted to conceptualize insight in psychosis while acknowledging its elusive nature. In his 1934 essay “The Psychopathology of Insight,” Aubrey Lewis [2] described insight as the “correct attitude to a morbid change in oneself,” while noting that this definition is not final and that each of the terms—correct, attitude, morbid, change in oneself—calls for discussion. A major discussion did not immediately follow, and the systematic investigation of insight remained relatively neglected throughout much of the 20th century. For several decades following Lewis’s work, the assessment of insight relied primarily on impressionistic and anecdotal methods rather than systematic evaluation [3–7].

In 1989, McEvoy et al. [8] introduced the first structured insight scale, marking a significant advancement. Since then, various insight measures have emerged, encompassing cognitive, attitudinal, symptom-specific, and temporal aspects. These measures vary in their assessment approaches, ranging from binary to spectrum-based evaluations, and in perspective, whether self-assessed or clinician-rated.

Despite these advancements, a persistent gap remains between the theoretical conceptualization of insight and its clinical manifestation [9]. The concept of insight, as tentatively defined by Lewis, comprises both awareness of a change in experience and a judgment of what the change means and how it impacts one’s functioning and interaction with the world [10]. This complexity poses significant challenges for researchers and clinicians alike, with different scales focusing on different aspects of insight.

The varied use of the concept of insight highlights a lack of consensus on its definition and measurement. For instance, the RAISE study found that the Coordinated Specialty Care (CSC) program significantly improved insight compared to community care over two years, as measured by a single item from the PANSS, which conflates insight’s judgment and awareness components. In contrast, McEvoy et al. [11], found no improvement in insight among involuntarily committed schizophrenia patients, using the Insight and Treatment Attitudes Questionnaire (ITAQ), which assesses patients’ awareness of their mental disorder and the need for treatment, capturing both cognitive recognition and attitudinal acceptance. David et al. [12] reported significant fluctuations in insight among schizophrenia patients over time, measured by the Schedule for Assessment of Insight (SAI), which evaluates awareness of illness, relabeling of symptoms, and treatment compliance. These variations in measurement tools complicate comparisons across studies [13–15].

Given the critical role of insight in understanding and treating psychosis, there is a need for a comprehensive evaluation of existing insight measures. This systematic review aims to address the challenges in assessing insight in individuals diagnosed with psychosis by critically appraising the various measures employed. By doing so, we seek to provide clarity on the most psychometrically valid and clinically useful tools available, facilitating more consistent and comparable research in the future.

This review will focus on answering the following question: What are the psychometric properties of measures that have been employed to assess insight in individuals diagnosed with psychosis? By conducting this systematic review, we aim to provide researchers and clinicians with a comprehensive understanding of the strengths and limitations of existing insight measures. This knowledge will inform the selection of appropriate tools for future studies and clinical assessments, ultimately contributing to more robust and comparable research in the field of psychosis.

Methods

The Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) statement has been followed in the reporting of this systematic review protocol [16]. The completed PRISMA-P checklist can be found in S1 Table.

Literature searches

An experienced medical librarian (MCF) will be consulted on methodology and a medical subject heading (MeSH) analysis of known articles provided by the research team will be done using the Yale MeSH Analyzer [mesh.med.yale.edu/]. Scoping searches will be performed in each database, and an iterative process will be used to translate and refine the searches.

To maximize sensitivity, the formal search will use controlled vocabulary terms and synonymous keywords to capture the concepts of "psychosis", "insight", and "measurements". Results will be limited to publications in English, but no date limits will be imposed on the search. This approach will ensure a comprehensive review of the literature, including early conceptualizations of insight in psychosis.

The search strategy will be peer-reviewed by a second librarian not otherwise associated with the project, enhancing the rigor of our methodology. To ensure comprehensive coverage, reviewers will check for additional relevant citing articles using included studies. To capture recently published articles, a second database search will be rerun before publishing the paper, ensuring the inclusion of the most up-to-date research.

The search consists of five search strategies combined with the ‘AND’ Boolean operator, focusing on:

1. Disorders: ‘Schizophrenia Spectrum and Other Psychotic disorders’, ‘psychosis’, ‘psychoses’, ‘psychotic’, and ‘schizo*’
2. Assessment: ‘assessment*’, ‘checklist*’, ‘Interview Psychological’, ‘instrument*’, ‘inventor*’, ‘measure*’, ‘questionnaire*’, ‘scale*’, ‘score*’, ‘survey*’, ‘test’, ‘tests’, ‘tool*’, ‘Surveys and Questionnaires’
3. Insight: ‘insight*’ and ‘awareness*’
4. Illness Awareness: ‘illness awareness*’
5. Illness Attitudes/Beliefs: ‘illness attitudes*’ and ‘illness beliefs*’

The searches will be conducted in five electronic databases. These databases include Ovid MEDLINE ALL, APA PsycInfo (Ovid), Embase (Ovid), Web of Science Core Collection (Clarivate), and Health and Psychosocial Instruments Database (HaPI) (Ovid). Each database will be systematically searched to identify pertinent research articles, ensuring a broad collection of literature relevant to the topic. As an example, the full search strategy that will be used in Ovid MEDLINE ALL can be found in Table 1.

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Table 1. Comprehensive search strategy for Ovid MEDLINE ALL.

https://doi.org/10.1371/journal.pone.0316447.t001

All identified citations will be imported into EndNote 21 and deduplicated using the Yale Reference Deduplicator tool [library.medicine.yale.edu/reference-deduplicator]. The deduplicated list will then be imported into Covidence [covidence.org] for the screening process.

Study selection

Following the initial search (stage 1), two more stages will follow (Fig 1).

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Fig 1. Flow diagram of the study selection process.

https://doi.org/10.1371/journal.pone.0316447.g001

Synthesis of results

We will prepare a comprehensive table of characteristics for all included studies, detailing information on study design, sample characteristics, insight measurement instrument(s), and reported outcomes. This table will provide a clear overview of the existing literature on insight measures in psychosis.

Outcome tables will be prepared for each insight measurement instrument (e.g., the Scale to Assess Unawareness of Mental Disorder, the Beck Cognitive Insight Scale) and each outcome construct (e.g., clinical insight, cognitive insight) separately. These tables will summarize the psychometric properties reported for each measure, including reliability, validity, responsiveness, and interpretability.

We will also create a table categorizing insight measures according to their primary focus or dimension of insight assessed, such as awareness of illness, attribution of symptoms, need for treatment, cognitive insight (self-reflectiveness and self-certainty), and multidimensional measures.

To provide a comprehensive overview, we will develop a quality matrix. This matrix will list all included insight measurement instruments and summarize key information including the type of measure (self-report, clinician-rated, or multi-informant), number of studies using the measure, population characteristics (e.g., diagnosis, age range, illness duration), COSMIN quality scores for each psychometric property (using the 4-point rating scale), and overall strength of evidence (based on GRADE approach). This quality matrix will allow readers to quickly identify the most appropriate insight measurement instruments with the strongest psychometric properties for different contexts and populations within psychosis research.

We will also present a narrative synthesis discussing our findings. This synthesis will summarize the overall state of insight measurement in psychosis, discuss strengths and limitations of existing measures, identify gaps in the current evidence base, provide recommendations for the use of insight measures in different research and clinical contexts, and suggest directions for future research in insight measurement.

This comprehensive approach to data synthesis and presentation will provide a clear, accessible, and informative overview of the current state of insight measurement in psychosis, facilitating evidence-based selection of measures for future research and clinical practice.

Discussion

In this protocol, we have outlined our approach for a systematic review of the measurement properties of instruments used to assess insight in individuals with psychosis. This comprehensive overview is crucial for several reasons. Insight in psychosis is a complex and multidimensional construct that has been conceptualized and measured in various ways over the years. The evolution of our understanding of insight necessitates a thorough evaluation of existing measurement tools to ensure they accurately capture the current conceptualization of insight in psychosis.

There is significant heterogeneity in the presentation of psychosis across individuals, which may influence the manifestation and assessment of insight. Factors such as illness duration, symptom severity, and cognitive functioning can all impact an individual’s level of insight, underscoring the need for measures that can capture this variability.

Insight in psychosis has important clinical implications. It has been associated with treatment adherence, clinical outcomes, and functional recovery. Therefore, having psychometrically sound measurement instruments is crucial for both research and clinical practice. These tools need to be reliable, valid, and sensitive to change to accurately assess insight and monitor its fluctuations over time or in response to interventions.

The assessment of insight often relies on both self-report and clinician-rated measures. Each approach has its strengths and limitations, and a comprehensive review of available tools is necessary to guide researchers and clinicians in selecting the most appropriate measures for their specific needs and contexts.

Currently, there is growing interest in personalized approaches to the treatment of psychosis, with insight being recognized as a potential target for intervention. Accurate measurement of insight is the critical first step in determining the need for such interventions and evaluating their effectiveness. When insight is not adequately assessed, opportunities for targeted interventions may be missed, potentially impacting patient outcomes.

To address these needs, we have initiated this systematic review aimed at improving the assessment and understanding of insight in psychosis. This review of the literature describing insight measurement instruments is a crucial step toward formulating evidence-based recommendations for both research and clinical practice.

By providing a comprehensive overview of available insight measures, their psychometric properties, and their applicability in different contexts, we aim to facilitate more informed decision-making in the selection and use of these tools. This, in turn, will contribute to more robust research in the field and potentially lead to improved clinical assessment and care for individuals with psychosis.

In conclusion, this systematic review will fill an important gap in the literature by synthesizing the current evidence on insight measurement in psychosis. The findings will not only inform future research but also have practical implications for clinical assessment and intervention planning in the care of individuals with psychosis.

Supporting information