Anomalous self-experience, or the experience of the self, are frequently present but underexplored in patients with schizophrenia. Unfortunately, to date, there are no available inventories in Spanish to assess these self-experiences. The present study aims to adapt and validate the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE) in the Spanish population.
MethodsA total of 171 participants were included: 112 cases (patients) and 59 healthy controls. Among them, 87 patients were diagnosed with schizophrenia (70 chronic and 17 first-episode patients) and 25 patients with bipolar disorder. The participants were evaluated using the structured clinical interview DSM-IV and were tasked with completing the Spanish version of the IPASE. The properties of the scale were analysed in terms of internal consistency, stability, and correlation between scores on the subscales with sociodemographic and clinical variables.
ResultsThe IPASE showed good reliability (Cronbach's alpha coefficient of 0.847) and intraclass correlation,with a value of 0.837 for the patient group and 0.812 for the control group. The variables of age and sex did not significantly correlate with the total IPASE score. Compared to healthy controls, cases obtained significantly higher overall scores on the IPASE and its five subscales; total scores on the IPASE (Cases: (20.96 ± 42.5)vs. control:(80.56 ± 20.6), p < 0.001).
ConclusionsThe Spanish version of the IPASE scale shows good psychometric properties in terms of reliability and validity for its application in assessing alterations in subjective self-experiences in patients with schizophrenia. This demonstrates the value of the IPASE as a tool in both clinical practice and research.
Anomalous self-experiences are disturbances in the subjective experience of the self prevalent in patients with schizophrenia1, including in the early stages2, which tend to remain stable throughout the course of the illness.3
The study of anomalous self-experiences, dates back to the early theoretical formulations of schizophrenia.4,5 In this context, phenomenology (as a discipline interested in the description and explanation of the structure of human experience of “being in the world”6,7) offers a renewed understanding of schizophrenia.8
Schizophrenia is defined as a disorder of self-experience or ipseity8, with ipseity understood as the basic sense of self, the center and core of one's own experience, which provides the central point of orientation for human beings, underlying motivation and the basis for organizing our experiential world according to our desires and needs.9
According to the framework developed by Sass and Parnas, the alteration of ipseity in schizophrenia revolves around three axes10,11,12: (I) hyperreflexivity, as intensified self-awareness of aspects of oneself that are normally implicit, tacit, or pre-reflective; (II) diminished sense of self, understood as a decrease in the intensity or vitality of one's own subjective presence; (III) alteration of the consciousness of the world, or loss of perceptual articulation and vital contact with reality, including others, so that the world appears decontextualized.8
Based on this phenomenological model, anomalous self-experiences in schizophrenia have been explored in numerous studies using the semi-structured interview EASE (Examination of Anomalous Self-Experience)2,13,14, which currently constitutes its main measurement instrument.14 The limitation of EASE is that it is a phenomenological interview that requires trained and highly qualified evaluators15, necessitating a considerable exploration time. Therefore, to have a relatively short and self-administered instrument for evaluating these anomalous self-experiences for application in research and clinical practice, the Inventory of Psychotic-like Anomalous Self-Experiences (IPASE) was developed.15 At present, a version in Spanish for neither the EASE nor IPASE instruments exists. Thus, we deemed it useful to undertake the validation of the latter.
The IPASE instrument is a self-administered scale consisting of 57 items in which participants indicate their degree of agreement with statements on a Likert scale, ranging from 1 (Completely Disagree) to 5 (Completely Agree). It has a five-factor structure. The first factor, Cognition, includes elements related to difficulties with thought processes, such as thought interference. The second factor, Self-awareness and Presence, contains items related to basic loss of self or identity and loss of connection with the world. The third factor, Awareness, includes items about alterations in time experience, alterations in intentionality, and difficulty distinguishing between imagination and reality. The fourth factor, Somatization, includes items involving alterations in bodily experiences, such as feeling the body changing shape or being difficult to control, thoughts of not feeling physically present or embodied. The last factor, Delimitation/Transitivism, contains items related to a boundary that disintegrates between the self and the world or a sense of non-existence.15 The inventory provides a score for each subscale, as well as a total score.
Research conducted using this self-report (IPASE) indicates the following discrepancies: (i) invariance in scores between genders; (ii) positive correlations with psychotic-like experiences and self-awareness, and negative correlations with self-report and measures of self-concept clarity and self-esteem; (iii) higher scores in participants with positive schizotypy compared to comparison groups and negative schizotypy; (iv) higher scores in patients with schizophrenia compared to healthy controls.15 This instrument has high internal reliability (α = 0.97).16
The correlation of scores obtained between the IPASE and EASE instruments is very high (r = 0.92).16 EASE domains 1 to 3 showed strong correlations with each of the IPASE subscales, and domains 4 and 5 showed moderate correlations with IPASE subscales. The correlation between these IPASE and EASE is stronger than that observed between IPASE and other symptom scales (CAARMS, BPRS, and SANS), demonstrating both convergent and discriminant validity.16
The aim of this study was to develop the Spanish-translated version of the IPASE scale and to test the validity and reliability of this inventory adaptation in patients with schizophrenia and healthy controls.
Materials and methodsStudy designThis is a naturalistic adaptation and validation study conducted in Spanish. It was approved by the Research Ethics Committee of the Clinical Hospital of Valladolid PI-22–2623. All participating subjects provided written informed consent. Participants were not remunerated nor provided with any other incentives to participate in the study. The questionnaire was administered in a single session, lasting 40–60 min, by the same evaluator and under stable environmental conditions.
ParticipantsThe study cohort was comprised of 171 subjects.: 112 patients (mean age 38 years; 68 men and 44 women), of whom 87 were diagnosed with schizophrenia (70 chronic and 17 first-episode patients), and 25 patients with bipolar disorder. Additionally, 59 healthy controls were recruited (mean age 33.98 years; 29 men, 30 women).
Patients were diagnosed by one of the psychiatrists in the group (their reference psychiatrist in most cases) according to the criteria of the Diagnostic and Statistical Manual of Mental Disorders (5th edition). All patients were receiving stable doses of atypical antipsychotics.
The exclusion criteria for both samples included a history of neurological illness (including head injuries with loss of consciousness), current or past substance abuse (except nicotine and caffeine), and an intellectual quotient (IQ) below 70. For the control group, subjects with a history of (or current) mental illness and treatment were excluded.
InstrumentsDemographic and clinical data of the participants were obtained and analysed using the following assessment instruments: Structured Clinical Interview for DSM-IV and the Spanish adaptation of the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE).
First, to verify the absence of mental illness in the control group, participants underwent the Structured Clinical Interview for DSM-IV (SCID: First, Spitzer, Gibbon, & Williams, 1998).17 Next, for the adaptation of the IPASE into Spanish, the guidelines of the International Test Commission for test adaptation were followed.17 Initially, permission was obtained from the authors of the original version. The translation process involved three independent forward translations (conducted by mental health professionals). These translations were then compared, and in cases of disagreement, the version closest to the original was chosen. The Spanish version was then translated back into English by a bilingual individual with specific training in mental health, who was not part of the initial translation team and had not seen the original version.
Some modifications were introduced in the new version, including the addition of the phrase “como si” (as if) to maintain the appropriate connotation of the items compared to the original version.
Statistical analysisStatistical analysis was conducted using IBM SPSS Statistics software (version 26.0). The same analysis as that performed in the validation of the English version was conducted.15 For the total score of the inventory and for each of the five subscales composing it, internal consistency was analysed using Cronbach's alpha coefficient and intraclass correlation. The following comparisons and correlations were then carried out: IPASE scores were compared between patients and controls using a Student's t-test, as well as between diagnoses (bipolar vs schizophrenia). The relationship between the total IPASE score and sociodemographic variables was analysed using Pearson's correlation coefficient for the age variable and comparing this score according to participants’ gender (t-test for independent samples) and level of education (using ANOVA and post hoc analysis for mean comparison).
ResultsDescriptive statisticsThe study cohort was comprised of 171 subjects: 112 patients (mean age 38 years; 68 men and 44 women), of whom 87 were diagnosed with schizophrenia (70 chronic and 17 first-episode patients), and 25 patients with bipolar disorder. Additionally, 59 healthy controls were recruited (mean age 33.98 years; 29 men, 30 women). All the variables and clinical characteristics of each group (patients and controls) are shown in Table 1.
Socio-demographic and clinical variables of the sample cohort.
SD: standard deviation.
The Spanish version of the IPASE achieved an overall Cronbach's alpha coefficient of 0.847. High consistency (intraclass correlation) was achieved in the measurements of both groups, with a value of 0.837 for the patient group and 0.812 for the control group. A summary of the intraclass correlation coefficient in the patient (case) and control groups is provided in Table 2.
Intraclass correlation.
df1: Degrees of freedom numerator; df2: Degrees of freedom denominator; Sig: Significance.
According to the results, the IPASE subscales demonstrated a high, positive correlation (Table 3), with the ego boundary subscale obtaining the lowest correlation among the subscales evaluated.
IPASE subscales correlation.
The comparison between men and women in both groups did not show statistically significant differences, with a chi-squared value of 0.15: (i) control group: males (79.55 ± 19.2) and females (81.53 ± 22.1) with a non-significant p-value; (ii) patients: males (119.9 ± 40.4); females (123.98 ± 45.8) with a non-significant p-value. Age did not show a significant relationship with the total IPASE score (0.179), neither in the patient (case) group (0.147) nor in the control group (‒0.032). Although no significant differences were observed in terms of educational level in the control group, significant differences were found in the cases (p = 0.088). Differences were identified in the analysis of mean comparison between the groups according to the level of education.
Relationship with clinical variablesCompared to the healthy controls, cases were found to achieve higher total scores on the IPASE (120.96 ± 42.5 vs. 80.56 ± 20.6, p < 0.001), as well as higher scores on the five subscales: Cognition (13.51 ± 6.3 vs. 8.54 ± 3.0, p < 0.001); Self-awareness (46.33 ± 18.3 vs. 30.24 ± 8.1, p < 0.001); Consciousness (14.75 ± 6.2 vs. 10.93 ± 4.4, p < 0.001); Somatization (37.04 ± 12.9 vs. 24.24 ± 7.1, p < 0.001); Demarcation/Transitivism (9.34 ± 4.0 vs. 6.61 ± 1.791, p < 0.001), with statistically significant values in all of them. Comparison between cases of schizophrenia vs. bipolar disorder did not yield significant differences in the total score of the IPASE (121.67 ± 41.7 vs. 118.52 ± 45.9; p = not significant), nor in any of its subscales: Cognition (13.82 ± 6.2 vs. 12.4 ± 6.4); Self-awareness (46.37 ± 17.8 vs. 46.2 ± 20.2); Consciousness (15.0 ± 6.1 vs. 13.84 ± 6.4); Somatization (37.05 ± 12.8 vs. 37 ± 13.4); Demarcation/Transitivism (9.43 ± 4.1 vs. 9.04 ± 3.8), with non-significant p-values in all five subscales.
DiscussionThe objective of the present study was to validate the Spanish version of the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE)15 to facilitate the assessment of anomalous self-experiences among Spanish individuals. Initially, following the guidelines of the International Test Commission18 for test adaptation, a linguistically and conceptually equivalent version of the original inventory was obtained.
The process and characteristics of the study population sample used for the validation of the Spanish version followed the model of Study 4 of Validation in a clinical sample, which constitutes the phase of the validation process carried out in the Development and Validation of The Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE).15 The scores on the IPASE instrument have shown to have adequate psychometric properties. Regarding internal structure, the results of this study are consistent with those obtained in the original version. Based on these results, the Spanish version of the IPASE can be considered a reliable and valid inventory for assessing anomalous self-experiences among individuals with schizophrenia in the Spanish population.
Higher scores on the inventory indicate a greater presence of anomalous self-experiences. As expected, and in line with previous results in Anglo-Saxon populations, individuals with schizophrenia obtained higher scores on the IPASE than healthy controls, similar to the validation study of the inventory. The analyses showed a stable structure for IPASE scores between men and women, with no significant differences in total scores or its subscales regarding gender variable in cases or controls. Similarly, no significant correlation was observed in terms of age with the IPASE score in either group, nor was such a correlation observed in terms of the level of education in the control group.
Although anomalous self-experiences have been described in the spectrum of schizophrenia, these are less studied in other psychiatric syndromes. Therefore, given our relatively small sample of patients with bipolar disorder, further studies are needed with samples from different clinical groups to assess their specificity (e.g. first-episode psychosis vs. chronic schizophrenia or at-risk individuals). In relation to the sample size of bipolar patients, we cannot rule out the presence of more severe alterations of self-experience among the cases with schizophrenia. To this end, it would be necessary to determine whether IPASE scores fluctuate over time via test‒retest studies to determine if increases in scores correlate with increases in positive and negative symptom scores.
A limitation of this inventory, which has been discussed in its English validation, refers to the difficulty in evaluating psychotic-like anomalous experiences due to the idiosyncrasy of the subjects themselves. Despite these limitations, the current preliminary data suggest the potential utility of the Spanish-version IPASE in clinical and research contexts for detecting or assessing alterations in ipseity.19
In conclusion, the Spanish version of the IPASE instrument provides satisfactory psychometric properties, including high internal consistency, concurrent validity, and good general and domain-specific discriminant validity. It is a simple, easy-to-use, and quick-to-apply inventory, making it a reliable and practical tool for assessing psychotic-like anomalous self-experiences in Spanish-speaking patients with schizophrenia, constituting a good instrument for use in clinical practice and research.