Sayaka Nishiura1,2Dai Miyawaki1,3*Kaoru Hirai2Ayaka Sukigara2Yui Kakishita4Koki Inoue2
Introduction: Hallucinations are serious symptoms that can lead to high levels of distress, functional impairment, and increased risk of suicide in both adults and children. However, their etiology and treatment remain unclear. Hallucinations and sensory processing difficulties (SPDs) are associated with various psychiatric disorders, including mood, anxiety, and post-traumatic stress disorder. This study aimed to investigate the potential association between hallucinations and SPDs in a pediatric population.
Methods: We conducted a cross-sectional study with 335 children aged 6–18 years who visited the child psychiatry outpatient clinic at Osaka Metropolitan University Hospital between April 2020 and March 2023 and continued treatment for at least three months. After excluding those with intellectual disabilities or uncontrolled epilepsy, 304 participants were included in the analyses. The presence of hallucinations was assessed through interviews with the children and their parents. SPDs were evaluated using the Short Sensory Profile. Binomial logistic regression analysis was conducted to assess the association between hallucinations and SPDs, adjusting for age, sex, autism spectrum disorder, socioeconomic difficulties (low-income, single-parent households), and the presence of mood and anxiety disorders.
Results: Hallucinations were present in 64 children (21%). Logistic regression analysis showed a significant positive association between SPDs and hallucinations, even after adjusting for age, sex, autism spectrum disorder, socioeconomic difficulties, and the presence of mood and anxiety disorders (odds ratio, 1.02; 95% CI, 1.008–1.036; p = 0.002).
Conclusion: The results of this study suggest a potential association between hallucinations and SPDs in pediatric patients. Further prospective studies are needed to explore the causal relationship between these factors and determine whether interventions for SPDs can alleviate hallucinations in children.
Hallucinations are defined as “perceptions that are not perceived by others” in the Diagnostic and Statistical Manual of Mental Disorders-5, Text Revision (DSM-5-TR) (1) and are common symptoms in the general population during childhood and adolescence. According to a systematic review, approximately 12% of children and adolescents in the general population have reported experiencing hallucinations (2). Although many benign hallucinations are observed during normal developmental processes, their presence in clinical cases is associated with high distress and functional impairment and may increase the risk of suicide (3–6). Previous studies have shown that hallucinations are observed not only in schizophrenia but also in various mental disorders such as mood disorders, anxiety disorders, post-traumatic stress disorder (PTSD), autism spectrum disorder (ASD), and obsessive-compulsive disorder (7–9). However, even when hallucinations are present, treatment often prioritizes comorbid mental disorders, and direct treatment for hallucinations is rarely provided (10). Exploring the common triggers and factors associated with hallucinations in these mental disorders may be useful in identifying preventive measures and coping strategies.
Additionally, sensory processing difficulties (SPDs) have been adopted as diagnostic criteria for ASD in the DSM-5-TR; however, they are also present in various mental disorders, including mood disorders, anxiety disorders, PTSD, and neurocognitive disorders (11). Sensory processing is influenced by both neurological and psychological factors, and the complex interaction between these two aspects means that the interpretation of the same stimulus can vary from person to person and may be inconsistent within the same individual. These sensory differences, which result in behavioral and emotional responses with difficulties in processing sensory stimuli, are referred to as sensory processing disorders (12). SPDs are assessed in clinical settings using the Short Sensory Profile (SSP), which comprehensively and efficiently evaluates the extent of SPDs using a 38-item questionnaire (13, 14). Recent studies have reported that hallucinations may be associated with common neurological mechanisms in SPDs. Parham et al. have found that individuals at high clinical risk for psychosis exhibit significant sensory processing differences that are associated with abnormalities in brain structure and connectivity, particularly in the thalamus and cortical regions (15). There have also been reports of altered neural connectivity and sensory-gate dysfunction in individuals with ASD, leading to SPDs (16, 17). Based on these findings, we hypothesized that SPDs may result from neurological mechanisms common to hallucinations, including impaired neural connectivity and sensory-gate dysfunction.
Interventions such as sensory integration and cognitive behavioral therapies are useful in reducing SPD-related distress (18, 19). If the relationship between SPDs and hallucinations is clarified, it may be possible to explore whether SPD treatment contributes to a reduction in hallucinations. Therefore, this cross-sectional study investigated the relationship between hallucinations and SPDs in patients attending a pediatric psychiatric outpatient clinic. The aim of our study was to test our hypothesis that SPDs are associated with hallucinations in children and adolescents.
This study included 335 children aged 6–18 years who consecutively visited the pediatric psychiatric outpatient clinic of Osaka Metropolitan University Hospital between April 2020 and March 2023 and continued their visits for over three months. Children with intellectual disabilities (n = 25, Intelligence Quotient < 70 on the Wechsler Intelligence Scale for Children-IV) and poorly controlled organic diseases such as epilepsy (n = 6) were excluded, leaving 304 children and their parents as participants. Socioeconomic status was assessed through interviews to determine family income and whether either parent was absent. Households receiving welfare or with an annual income below three million yen (approximately $19,000) were considered low-income households. The self-reports of those diagnosed after visiting a psychiatrist formed the basis for establishing the presence of parental mental illness. Written informed consent was obtained from all children and their guardians. The Ethics Committee of the Graduate School of Medicine, Osaka Metropolitan University, reviewed and approved the study protocol. The study was conducted in accordance with the principles of the Declaration of Helsinki.
Information was obtained through interviews and questionnaires. The presence of hallucinations was confirmed by the children and their parents during the examination using the following questions: “Did you hear sounds or voices that did not seem to exist to others within the last six months?” and “Did you see things that did not seem to exist to others within the last six months?” In cases of discrepancies between the responses of the children and those of their parents, experienced pediatric psychiatrists made the final judgment after detailed questioning. The SSP was used to evaluate SPDs (14). The SSP is a 38-item questionnaire divided into seven subscales (tactile sensitivity, taste/smell sensitivity, movement sensitivity, under responsiveness/seeks sensation, auditory filtering, low energy/weakness, and visual/auditory sensitivity), with higher scores indicating a higher severity of SPDs. The standardized Japanese version extends the target age to three years and older (20). The Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children—Present and Lifetime Version (K-SADS-PL) is a semi-structured interview used to diagnose mental disorders based on the DSM-IV-TR criteria (21). The Japanese version of the K-SADS-PL-J has demonstrated consistent reliability and validity across studies (22). Experienced psychiatrists used the DSM-5 criteria to diagnose ASD because the K-SADS-PL-J does not include diagnostic criteria for ASD.
Participants with (n = 64) and without (n = 240) hallucinations were compared. Descriptive statistics (means, standard deviations, medians, ranges, and proportions) were calculated for the demographic and clinical variables. Pearson’s chi-square test and Fisher’s exact test (for expected values less than five) were used for categorical variables, whereas Student’s t-test or Mann–Whitney U test (depending on the normality of the variable) were used for continuous variables. Additionally, we compared demographic characteristics and SSP scores among three groups: auditory hallucinations only, visual hallucinations only, and both. Chi-square tests or Fisher’s exact tests were used for categorical variables, whereas the Kruskal-Wallis test was used for continuous variables. A binary logistic regression analysis was performed using the forced entry method, with the presence or absence of hallucinations as the dependent variable, and adjustments were made for potential confounding factors identified in previous studies (age, sex, low-income household, single-parent household, ASD, mood disorders, and anxiety disorders). This analysis was conducted to test the hypothesis that the association between SPDs and hallucinations remains significant even after controlling for the effects of these independent variables. Variables other than age were converted into dummy variables (1 for males or the presence of characteristics and 0 for females or the absence of characteristics). For all independent variables, the variance inflation factor values were below 10, indicating that multicollinearity was not a concern in this analysis. Statistical analysis was performed using SPSS (version 26.0.0). Statistical significance was defined as a two-sided p-value < 0.05.