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Psychotic-like experiences and associated socio-demographic factors among adolescents in China
SCHRES-06394; No of Pages 6 Schizophrenia Research xxx (2015) xxx–xxx
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Psychotic-like experiences and associated socio-demographic factors among adolescents in China Meng Sun a, Xinran Hu b, Wen Zhang a, Rui Guo a, Aimin Hu a, Tumbwene Elieza Mwansisya c, Li Zhou a, Chang Liu a, Xudong Chen a, Xiaojun Huang a, Jingcheng Shi d, Helen F.K. Chiu e, Zhening Liu a,⁎ a
Institute of Mental Health, The Second Xiangya Hospital of Central South University, Changsha, China School of Medicine and Institute for Public Health, Washington University, St. Louis, USA College of Health Sciences, University of Dodoma, P.O. Box 395, Dodoma, Tanzania d School of Public Health, Central South University, Changsha, China e Department of Psychiatry, Chinese University of Hong Kong, Hong Kong, China b c
a r t i c l e
i n f o
Article history: Received 29 January 2015 Received in revised form 6 May 2015 Accepted 19 May 2015 Available online xxxx Keywords: CAPE Psychosis Trauma history Left-behind children
a b s t r a c t Objective: Adolescents with persistent psychotic-like experiences (PLEs) may be at high risk for later development of psychoses. Exploring early age risk factors for PLEs may provide useful information for prevention of mental disorders and improvement of mental health. Method: A total of 5427 adolescents (aged between 10 and 16) participated in a cross-sectional survey, with social and demographic information collected. The Positive Subscale of Community Assessment of Psychic Experiences (CAPE) was used to measure PLEs, and the CAPE Depressive and Negative Subscales were used to examine depressive and negative experiences. The Trauma History Questionnaire (child version) was used to assess experiences of previous traumatic events. Results: In our study, 95.7% of the adolescents reported more than one episode of PLEs, while 17.2% reported “nearly always” having PLEs. High positive correlations were shown both between frequency scores among experiences of three dimensions (PLEs, depressive and negative experiences), and between frequency and distress scores. Factors associated with a higher risk for more frequent and distressing PLEs include: urban setting, family history of psychiatric illnesses, and higher impact from previous traumatic events at present. Conclusions: Episodes of PLEs are common in Chinese adolescents, however only a small proportion have persistent PLEs, with worsening distress as the frequency increased. PLEs shared similar environmental and genetic risk factors not only with the clinical phenotypes, which is consistent with the continuity model of PLEs, but also with depressive and negative experiences, which may imply etiologic relation between different dimensions of psychosis at the subclinical level. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Psychotic-like experiences (PLEs) are common in childhood and adolescence, and mostly transient in nature. However, it may persist in a small population before developing further into clinical psychoses (van Os et al., 2009; Dominguez et al., 2011). Data shows that nearly half of all lifetime mental disorders start by mid-adolescence (Kessler et al., 2005, 2007), which indicates that adolescence is an important period in development of mental disorders. Therefore, exploring the risk factors of PLEs at this early age may provide useful information in understanding the development of mental disorders and throw light on the prevention of mental disorders. PLEs are defined as experiences that resemble the positive symptoms of psychosis as encountered in clinical samples but which do not ⁎ Corresponding author. Tel.: +86 731 85292136; fax: +86 731 85292470. E-mail address: [email protected] (Z. Liu).
cause the levels of distress or impairment that would lead to clinically significant distress, disability or loss of functioning. Two continuity models have been proposed on PLEs. The quasi-dimensional model conceptualizes PLEs as forme frustes or variants of mental disorders (Meehl, 1962, 1989), while the fully dimensional model of psychosis proposes that PLEs are part of personality (Claridge, 1972, 1994). Preliminary evidence has suggested that in a minority of individuals PLEs in childhood and adolescence may be risk factors for later psychiatric disorders and poor psychosocial outcome (Dhossche et al., 2002; Hanssen et al., 2005; Kaymaz et al., 2012). The risk for transition to psychosis is associated with the degree of PLEs' persistence, associated distress, and the severity of PLEs (Wigman et al., 2011). However, few studies have explored the associated psychosocial factors and psychopathological difficulties in young people at a crucial age (Lataster et al., 2006; Nishida et al., 2008; Armando et al., 2012; Fisher et al., 2013). In order to assess the prevalence of PLEs in our study, we selected the Positive Subscale of Community Assessment of Psychic Experiences
http://dx.doi.org/10.1016/j.schres.2015.05.031 0920-9964/© 2015 Elsevier B.V. All rights reserved.
Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
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M. Sun et al. / Schizophrenia Research xxx (2015) xxx–xxx
(CAPE). Previous research found that there was evidence for the existence of PLEs and depressive and negative experiences in the general population and significant correlations between them, which suggest they may share similar risk factors (Stefanis et al., 2002). Longitudinal studies also show psychosis proneness is strongly associated with depression, suggesting that a continuum of vulnerability may exist between psychotic disorders and affective disorders (Verdoux et al., 1999). Therefore we also explored characteristics and risk factors of the depressive and negative experiences with Depressive and Negative Subscales of CAPE. During the past 30 years, there is a massive migration of residents of rural areas to work in the urban areas in China. By the end of 2013, the number of internal migrants in China amounted to 245 million. As a result, there are many “left-behind” children, referring to the children and adolescents left behind in hometown by one or both of their migrating parents (Jia and Tian, 2010). Recent estimates place the number of “left-behind” children in China as approximately 58 million (Jia and Tian, 2010; Ding and Bao, 2014). They endure severe stress caused by migration of parents. Data from recent studies show that they are at greater risk for developing mental disorders (He et al., 2012; Wang et al., 2014). In regard to urbanization, studies have demonstrated that being raised in urban area confers a greater risk of psychiatric disorders (Pedersen and Mortensen, 2001; Peen et al., 2010). Previous studies have indicated ethnic minority as a risk factor of PLEs (Morgan et al., 2009). Finally, a few studies have found positive correlation between childhood trauma and PLEs (Jeronimus et al., 2013; Matheson et al., 2013). Our study has two main aims. First, we would like to investigate the prevalence and characteristics of PLEs and depressive and negative experiences among adolescents in Hunan Province, China. Second, some potential genetic and environmental factors associated with more frequent and distressing PLEs were explored in order to provide useful information for mental disorder prevention. Unlike previous studies that usually evaluate childhood traumas in adulthood, our study evaluated the impact of childhood traumas during the period of childhood and adolescence, which may be more relevant. Besides, in order to identify children's distress in the acute aftermath of traumatic events, our study included their impact felt by the children, both at the time of the event and at the survey. 2. Method 2.1. Sample Eleven Middle schools in both Xiangxi Region and Changsha City of Hunan Province were sampled using random cluster method. A total of 5427 students of the first grade from Middle schools were surveyed. All participants and their parent/guardian gave written consent for the study. In general, it took 45 min for the students to fill in the questionnaires. The study was approved by the Ethics Committees of the Second Xiangya Hospital of Central South University. 2.2. Instruments Socio-demographic information to be collected included: gender, age, ethnicity, boarding options, residency status, sources of income, “left-behind” child status, divorced family, parental death, single child status, family history of psychiatric illnesses and past history of any psychiatric conditions for participants. Exclusion criteria for the study include participants with history of any psychiatric conditions and who had N25% of CAPE data missing. We excluded the children with history of psychiatric conditions according to the socio-demographic information in the questionnaires and provided by schools and teachers. The CAPE was used to evaluate the lifetime positive, depressive and negative experiences in the general population (Stefanis et al., 2002; Konings et al., 2006). This self-report instrument consists of 42 items
covering positive, depressive and negative dimensions (PD, DD and ND) on both a frequency scale (1 = never, 2 = sometimes, 3 = often, 4 = nearly always) and a distress scale (1 = not distressed, 2 = a bit distressed, 3 = quite distressed, 4 = very distressed). It includes 20 items of positive psychotic experiences derived from Peters et al. Delusions Inventory (PDI-21) (Peters et al., 1999), 14 items exploring negative experiences derived from an instrument of subjective experience of negative symptoms (SENS) (Selten et al., 1998), and 8 cognitive depressive experiences (Kibel et al., 1993). Previous results have indicated the CAPE to be stable, reliable and valid (Konings et al., 2006). In our study, PLEs were measured through items of PD in the CAPE, while depressive and negative experiences used items of DD and ND, respectively. To assess adolescents' histories of trauma, the Trauma History Questionnaire (THQ) child version (Stover et al., 2010) was used. The scale contains 15 items. Each item was designed to assess the child's history of traumatic events in the lifetime as well as the level of impact on the child, both at the time of the event and at present. Respondents can select a number from “not at all (0)” to “extremely (4)”. Both the Chinese version of CAPE and THQ child version were translated and validated for the first time. Both questionnaires showed good reliability and validity. The papers on the reliability and validity are now under preparation. 2.3. Analyses Analyses were conducted using IBM SPSS Statistics version 19.0. Descriptive statistics were performed for group characteristics. The prevalence was calculated both at the level of “at least sometimes” and “nearly always” respectively in all three dimensions. Frequency of each item was also counted. Correlation analysis was conducted through Pearson's correlation coefficient to investigate associations between frequency scores among the three dimensions, and then between frequency and distress scores. Due to the lack of generally acknowledged cut-off points separately in three dimensions, hierarchical linear cluster analyses were performed on the sample to get high, medium and low score groups. The whole sample was divided into three clusters according to both frequency and distress scores of each dimension, respectively. The same statistical method was also used for the THQ to divide the sample into three groups, respectively according to the level of impact at the time of the event and at present. To investigate the predictors of more frequent and distressing PLEs and depressive and negative experiences, we conducted ordinal logistic regression analyses to calculate odds ratios (ORs) and 95% confidence intervals (95% CI). We entered all dichotomous socio-demographic variables and levels of impact from previous trauma as independent variables, using age as covariate variable. We considered p-value less than 0.05 to be statistically significant. 3. Results 3.1. Description of the sample All 5427 students agreed to participate in our survey. A total of 131 participants who had N25% of CAPE data missing and 23 participants who had history of psychiatric conditions were subsequently removed from further analyses, leaving 5273 with valid data. These participants were aged between 10.0 and 16.6 years, and mean age was 12.6 years (SD = 0.627). Table 1 shows some of the other social-demographic characteristics. 3.2. Characteristics of experiences of three dimensions in the sample Almost all the adolescents in our sample experienced at least one CAPE item during lifetime (entire CAPE = 98.50%, PD (PLEs) = 95.66%, DD = 95.01%, ND = 94.06%). However, prevalence decreased sharply when the frequency increased to “nearly always” (entire
Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
M. Sun et al. / Schizophrenia Research xxx (2015) xxx–xxx Table 1 Descriptive statistics of social-demographic variables*.
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Table 2 Frequency of each item in the three dimensions of the CAPE.
Characteristics
%
Gender (female) Ethnicity (Han) Boarding options (at school) Residency status** (urban) Family has stable income?*** (no) “Left-behind” child status Divorced family Parental death Single child status Family history
48.8 48.7 24.9 34.5 6.6 19.9 4.5 1.3 32.1 3.0
Note: *All the variables are dichotomous. **Residency status represents urban or rural household registration. There is a strict household registration system in China, which divided residents into urban and rural. Rural residents are not able to enjoy the equal social benefits of urban residents, no matter how long they have lived or worked in the cities. ***Stable income means that the family has stable source of income and can support the family members without others' help. On the contrary, not having stable income means that the family needs help from other people or government aid.
CAPE = 26.74%, PD (PLEs) = 17.24%, DD = 7.53%, ND = 15.78%). Frequency of each item shares similar characteristics, but varied in different items (Table 2). Correlations between frequency scores in the three dimensions were positive and significant (p b .01) (Table 3). The positive correlation between frequency and distress scores for entire CAPE was significant and very strong (Fig. 1). The correlation was also very strong for PD (PLEs), DD and ND (r = 0.932, 0.932 and 0.920, p = .000 for all the above) 3.3. Factors associated with more frequent and distressing experiences of three dimensions The sample was divided into high, medium and low score groups respectively in three dimensions (Fig. 2). The groups were confirmed to be significant (p = .000) using the ANOVA method. No reason for potential multicollinearity of all variables was found, with the variance inflation factor (VIF) values of 1.26 and below (O'Brien, 2007). The results are presented in Table 4. In this sample, family history and higher impact from previous trauma at present predicted more frequent and distressing experiences of all three dimensions. Adolescents with urban household registration had more frequent and distressing PLEs and depressive experiences than their rural counterparts, while females and “left-behind” children had more frequent and distressing depressive and negative experiences. In addition, adolescents who had parental death experienced more frequent and distressing depressive experiences only. As impact from previous trauma at present showed high ORs in all three dimensions, further analysis of covariance was conducted between clusters of trauma impact and frequency scores of each CAPE dimension, using age as covariance (Table 5). In comparison between the two groups, symptoms from all three dimensions associated with medium trauma impact are significantly higher than low trauma impact (p b .05). However, there is no significant difference between medium and high trauma impact, which may be explained by the small sample size of the high trauma impact group. 4. Discussion A median prevalence of 17% (range from 5% to 35.3%) was reported in a recent review on PLEs (Kelleher et al., 2012). Only items on auditory hallucinations were chosen for the analysis in Kelleher et al.'s review, while our study examined a broader range of symptoms. It can explain why the prevalence in our study was much higher. However, when we examined items related to auditory hallucinations in our sample, the prevalence of the question “Do you ever hear voices when you are
Never (%)
At least sometimes (%)
Nearly always (%)
Positive dimension (PLEs) 2. Double meaning 5. Messages from magazines or TV 6. False appearance 7. Being persecuted 10. Conspiracy 11. Being important 13. Being special 15. Telepathy 17. Influenced by devices 20. Voodoo 22. Odd looks 24. Thought withdrawal 26. Thought insertion 28. Thought broadcasting 30. Thought echo 31. External control 33. Verbal hallucinations 34. Voices conversing 41. Capgras 42. Visual hallucinations
42.8 75.2 36.9 70.5 69.9 42.0 63.3 46.0 53.1 72.1 59.8 80.6 76.1 70.6 49.0 77.8 63.1 76.5 79.7 80.6
57.2 24.8 63.1 29.5 30.1 58.0 36.7 54.0 46.9 27.9 40.2 19.4 23.9 29.4 51.0 22.2 36.9 23.5 20.3 19.4
0.7 0.5 2.6 0.6 0.9 4.5 3.5 3.5 3.5 2.8 1.8 0.5 0.8 1.4 2.5 1.1 1.6 0.9 1.2 0.6
Depressive dimension 1. Sad 9. Pessimism 12. No future 14. Not worth living 19. Frequently cry 38. Guilty 39. Failure 40. Feeling tense
18.9 53.4 79.6 78.7 74.9 40.8 63.1 21.1
81.1 46.6 20.4 21.3 25.1 59.2 36.9 78.9
0.7 1.3 1.1 3.5 1.2 1.3 1.5 3.7
Negative dimension 3. Lack of enthusiasm 4. Not talkative 8. No emotion 16. No interest in others 18. No motivation 21. No energy 23. Empty mind 25. Lack of activity 27. Blunted feelings 29. Lack of spontaneity 32. Blunted emotions 35. Lack of hygiene 36. Unable to terminate 37. Lack of hobby
51.5 46.1 50.2 72.3 43.8 66.2 57.2 47.6 69.2 50.2 68.3 71.5 73.6 76.4
48.5 43.9 49.8 27.7 56.2 33.8 42.8 52.4 30.8 49.8 31.7 28.5 26.4 23.6
3.9 3.1 1.6 1.2 2.9 1.3 0.8 2.4 1.0 2.4 1.1 0.9 0.9 2.7
Note: CAPE, the Community Assessment of Psychic Experiences; PLEs, psychotic-like experiences.
alone” with a frequency of “at least “sometimes”, is 36.9%. This is compatible with the findings in the studies used in this meta-analysis. However, PLEs are common in adolescents, with a small proportion having frequent PLEs, which suggest that transient PLEs are not pathological. Therefore the focus of our study was the risk factors associated with more frequent and distressing PLEs. Our results showed more PLEs in adolescents with urban household registration, although they enjoyed more social benefits. Similarly, there is a higher prevalence of psychotic disorders in urban areas versus rural Table 3 Correlations between dimensions of the CAPE frequency scale.
PD (PLEs) DD ND CAPE total
PD (PLEs)
DD
ND
CAPE total
1 0.670** 0.614** 0.906**
1 0.710** 0.852**
1 0.869**
1
Note: ** p b .01. CAPE, the Community Assessment of Psychic Experiences; PD, positive dimension; PLEs, psychotic-like experiences; DD, depressive dimension; ND, negative dimension.
Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
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M. Sun et al. / Schizophrenia Research xxx (2015) xxx–xxx
Fig. 1. Relationship between frequency and distress scores for entire CAPE (r = 0.934, p = .000). CAPE, the Community Assessment of Psychic Experiences questionnaire.
Table 4 Logistic regression of predictors of more frequent and distressing experiences of three dimensions. Model PD (PLEs)
Gender Ethnicity Boarding options Residency status Stable income “Left-behind” child status Divorced family Parental death Single child Family history THQ1 THQ2
Model DD
Model ND
OR
(95%CI)
OR
(95%CI)
OR
(95%CI)
1.03 1.47 0.61 2.32** 1.08 1.45 1.63 2.62 0.96 2.62* 0.57 8.44***
(0.63, 1.69) (0.87, 2.49) (0.31, 1.19) (1.36, 3.96) (0.41, 2.83) (0.78, 2.72) (0.64, 4.19) (0.77, 8.96) (0.55, 1.69) (1.06, 6.46) (0.11, 2.98) (4.60, 15.50)
1.81** 0.95 1.02 1.55* 1.35 1.65* 1.18 2.73* 1.32 2.13* 1.05 4.92***
(1.24, 2.64) (0.63, 1.39) (0.68, 1.54) (1.04, 2.31) (0.73, 2.48) (1.08, 2.52) (0.54, 2.55) (1.09, 6.82) (0.87, 2.01) (1.04, 4.33) (0.30, 3.67) (2.84, 8.54)
1.49** 1.14 1.06 1.20 1.33 2.00*** 1.11 1.78 1.05 1.81* 1.48 3.31***
(1.16, 1.91) (0.89, 1.48) (0.81, 1.40) (0.91, 1.58) (0.88, 2.01) (1.52, 2.63) (0.63, 1.96) (0.82, 3.88) (0.79, 1.40) (1.09, 3.01) (0.61, 3.60) (2.14, 5.13)
Note: *p b .05, **p b .01, ***p b .001. PD, positive dimension; PLEs, psychotic-like experiences; DD, depressive dimension; ND, negative dimension; CI, confidence intervals; OR, odds ratio; THQ1 represents impact from trauma at the time of the event; THQ2 impact from trauma at present. Adjusted for age.
areas in some previous studies (Faris and Dunham, 1939; Mortensen et al., 1999; Peen et al., 2010). Epidemiologic research has documented the associations that particular features of the urban environment, such as concentrated disadvantage (i.e., areas characterized by high poverty, unemployment, and other socio-economical disadvantages), residential segregation, social disorganization, and less green space, contribute to the risk of psychotic disorders (Faris and Dunham, 1939; Galea et al., 2011; McKenzie et al., 2013). Recent studies attempting to explore the mechanism between urban areas and psychotic disorders, found that urban upbringing could impact brain architecture (Haddad et al., 2014), change the (re)activity of the HPA axis (Steinheuser et al., 2014), or make changes in DNA methylation (Galea et al., 2011). Although the exact mechanisms are unknown, harmful influence of urban environment may start as early as growing stage according to our study. It is well-known that having a family history of psychiatric illness is associated with elevated risk for developing psychotic disorders (Mortensen et al., 1999). Studies on monozygotic and dizygotic twins have also demonstrated that genetic contribution was apparent for self-reported PLEs in the general population (Lataster et al., 2009; Wigman et al., 2011). In our study we found individuals with family history tended to have more frequent and distressing PLEs. Therefore we
speculate that genetic influence may play an important role in aggravating severity of PLEs. A recent meta-analysis reported a medium to large effect of childhood adversity in people with psychosis (Matheson et al., 2013). However, there was no significant relation between PLEs and impact from trauma at the time of the event in our study, whereas adolescents who had more impact from previous trauma at present had a much higher risk of PLEs. Therefore we can infer that different changes have taken place in these adolescents after the trauma. As we have known, people's responses to trauma vary widely. Some develop mental Table 5 Comparison among different trauma impact groups at present on frequency scores of each dimension (mean ± SD).
PD (PLEs) DD ND
Low score group
Medium score group
High score group
p
28.55 ± 6.459 12.25 ± 2.938 20.77 ± 5.045
37.16 ± 8.995 15.63 ± 4.429 24.95 ± 6.685
35.22 ± 6.671 16.05 ± 2.162 21.91 ± 2.206
b.001 b.001 b.001
Note: SD, standard deviation; PD, positive dimension; PLEs, psychotic-like experiences; DD, depressive dimension; ND, negative dimension. Adjusted for age.
Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
M. Sun et al. / Schizophrenia Research xxx (2015) xxx–xxx
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Fig. 2. Results of cluster analyses in three dimensions. PD, positive dimension (or psychotic-like experiences); DD, depressive dimension; ND, negative dimension.
disorders or mild to moderate psychological symptoms that resolve rapidly, and others report no new psychological symptoms (Southwick and Charney, 2012). The different responses depend on different processes of adaptation in face of traumas, which can be called resilience. So it is not traumas themselves but the poor resilience of the subjects that leads directly to higher level of impact at present and results in more frequent and distressing PLEs finally. Resilience depends on numerous emotion regulation, social, physical health, cognitive factor, neurobiological risk and protective factors. Therefore early age cognitive behavioral therapy interventions, and measures on improving emotion regulation (i.e., delay gratification and frustration education) and physical health may be beneficial to prevention of psychotic disorders. However, there was no significant relation between PLEs and ethnicity in our study, which was thought to be a risk factor. Ethnic minority status is considered to be a risk factor of psychotic disorders, which may be explained by discrimination and rejection sensitivity (Anglin et al., 2014; Berg et al., 2014). The different result in our study may be partly interpreted as the result of policy for the protection of minorities in China. Most of the minority we investigated lived in the minority compact-communities, with no long-term experience of exclusion. “Left-behind” children, as a unique social phenomenon in contemporary China, have attracted increasing attention. Previous research found the “left-behind” children have lower self-concept and more mental health problems (He et al., 2012; Wang et al., 2014). However, no higher risk for PLEs, but depressive and negative experiences was found in our study. Loneliness (Jia and Tian, 2010), high risk for suffering abuse and bullying in schools caused by lack of care (Givaudan and Pick, 2013), may give rise to the frequent and severe depressive experiences. Lack of adequate family bonding, and enough time for school activities may cause lack of necessary mental stimulation in the critical period of brain development, which may result in more negative experiences. However, follow-up study is needed to find the internal relation between development of psychoses and “left-behind” children. In summary, similar to psychotic disorders, more frequent and distressing PLEs are probably associated with genetic factors as well as environmental factors, which are consistent with the continuity model of PLEs. The dimensional representation of the psychosis phenotype suggests that psychosis is the simultaneous variation of correlated symptom dimensions. However, this distribution of psychosis can extend into general population as well, which is proved in our study. The subclinical depressive and negative experiences also shared similar risk factors with the corresponding symptoms at the clinical level, which may further prove the continuum of psychosis in dimensional approach. In our study, there are also many overlapping risk factors in three dimensions, which can also be found between affective and non-affective psychotic syndromes. So it is attractive to speculate from the subclinical level that etiologic relation exists between different symptom dimensions of psychosis.
There are some limitations for the study. First, as self-reported questionnaires were used, and participants were very young, it is possible that some of the questionnaires were not carefully completed. So the findings of our study have to be interpreted with caution. Second, there were no strict exclusion criteria for participants who had history of psychiatric conditions, as we did not adopt structured instrument for making diagnoses. Third, family history of psychiatric illnesses is not necessarily due to genetic etiology as it can also be related to a shared environment, or other reasons. It may be helpful to improve the global mental health if we can identify adolescents with high-risk PLEs, and provide support or interventions for them from an early stage. However, further prospective studies are required to examine if PLEs in adolescence are associated with a higher risk to develop psychoses in adulthood, and we are planning to follow up our cohort of subjects prospectively to address this question. Role of funding source The work was supported by the National Natural Science Foundation of China (81271485, 81471362 to Z.N. Liu) and the Hunan Provincial Natural Science Foundation of China (07JJ3046 to Z.M. Xue). Contributors Authors Meng Sun, Xinran Hu, Wen Zhang and Zhening Liu designed the study and wrote the protocol. All authors participated in data collection. Authors Meng Sun and Jingcheng Shi undertook the statistical analysis, and author Meng Sun wrote the first draft of the manuscript. Authors Helen Chiu and Zhening Liu modified the manuscript. All authors contributed to and have approved the final manuscript. Conflict of interest None. Acknowledgments The authors would like to thank Dr. Eric Chen and Dr. Sherry Kit wa Chan from the University of Hong Kong. Both of them offered advice on the study design.
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Psychotic-like experiences and associated socio-demographic factors among adolescents in China Meng Sun a, Xinran Hu b, Wen Zhang a, Rui Guo a, Aimin Hu a, Tumbwene Elieza Mwansisya c, Li Zhou a, Chang Liu a, Xudong Chen a, Xiaojun Huang a, Jingcheng Shi d, Helen F.K. Chiu e, Zhening Liu a,⁎ a
Institute of Mental Health, The Second Xiangya Hospital of Central South University, Changsha, China School of Medicine and Institute for Public Health, Washington University, St. Louis, USA College of Health Sciences, University of Dodoma, P.O. Box 395, Dodoma, Tanzania d School of Public Health, Central South University, Changsha, China e Department of Psychiatry, Chinese University of Hong Kong, Hong Kong, China b c
a r t i c l e
i n f o
Article history: Received 29 January 2015 Received in revised form 6 May 2015 Accepted 19 May 2015 Available online xxxx Keywords: CAPE Psychosis Trauma history Left-behind children
a b s t r a c t Objective: Adolescents with persistent psychotic-like experiences (PLEs) may be at high risk for later development of psychoses. Exploring early age risk factors for PLEs may provide useful information for prevention of mental disorders and improvement of mental health. Method: A total of 5427 adolescents (aged between 10 and 16) participated in a cross-sectional survey, with social and demographic information collected. The Positive Subscale of Community Assessment of Psychic Experiences (CAPE) was used to measure PLEs, and the CAPE Depressive and Negative Subscales were used to examine depressive and negative experiences. The Trauma History Questionnaire (child version) was used to assess experiences of previous traumatic events. Results: In our study, 95.7% of the adolescents reported more than one episode of PLEs, while 17.2% reported “nearly always” having PLEs. High positive correlations were shown both between frequency scores among experiences of three dimensions (PLEs, depressive and negative experiences), and between frequency and distress scores. Factors associated with a higher risk for more frequent and distressing PLEs include: urban setting, family history of psychiatric illnesses, and higher impact from previous traumatic events at present. Conclusions: Episodes of PLEs are common in Chinese adolescents, however only a small proportion have persistent PLEs, with worsening distress as the frequency increased. PLEs shared similar environmental and genetic risk factors not only with the clinical phenotypes, which is consistent with the continuity model of PLEs, but also with depressive and negative experiences, which may imply etiologic relation between different dimensions of psychosis at the subclinical level. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Psychotic-like experiences (PLEs) are common in childhood and adolescence, and mostly transient in nature. However, it may persist in a small population before developing further into clinical psychoses (van Os et al., 2009; Dominguez et al., 2011). Data shows that nearly half of all lifetime mental disorders start by mid-adolescence (Kessler et al., 2005, 2007), which indicates that adolescence is an important period in development of mental disorders. Therefore, exploring the risk factors of PLEs at this early age may provide useful information in understanding the development of mental disorders and throw light on the prevention of mental disorders. PLEs are defined as experiences that resemble the positive symptoms of psychosis as encountered in clinical samples but which do not ⁎ Corresponding author. Tel.: +86 731 85292136; fax: +86 731 85292470. E-mail address: [email protected] (Z. Liu).
cause the levels of distress or impairment that would lead to clinically significant distress, disability or loss of functioning. Two continuity models have been proposed on PLEs. The quasi-dimensional model conceptualizes PLEs as forme frustes or variants of mental disorders (Meehl, 1962, 1989), while the fully dimensional model of psychosis proposes that PLEs are part of personality (Claridge, 1972, 1994). Preliminary evidence has suggested that in a minority of individuals PLEs in childhood and adolescence may be risk factors for later psychiatric disorders and poor psychosocial outcome (Dhossche et al., 2002; Hanssen et al., 2005; Kaymaz et al., 2012). The risk for transition to psychosis is associated with the degree of PLEs' persistence, associated distress, and the severity of PLEs (Wigman et al., 2011). However, few studies have explored the associated psychosocial factors and psychopathological difficulties in young people at a crucial age (Lataster et al., 2006; Nishida et al., 2008; Armando et al., 2012; Fisher et al., 2013). In order to assess the prevalence of PLEs in our study, we selected the Positive Subscale of Community Assessment of Psychic Experiences
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Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
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(CAPE). Previous research found that there was evidence for the existence of PLEs and depressive and negative experiences in the general population and significant correlations between them, which suggest they may share similar risk factors (Stefanis et al., 2002). Longitudinal studies also show psychosis proneness is strongly associated with depression, suggesting that a continuum of vulnerability may exist between psychotic disorders and affective disorders (Verdoux et al., 1999). Therefore we also explored characteristics and risk factors of the depressive and negative experiences with Depressive and Negative Subscales of CAPE. During the past 30 years, there is a massive migration of residents of rural areas to work in the urban areas in China. By the end of 2013, the number of internal migrants in China amounted to 245 million. As a result, there are many “left-behind” children, referring to the children and adolescents left behind in hometown by one or both of their migrating parents (Jia and Tian, 2010). Recent estimates place the number of “left-behind” children in China as approximately 58 million (Jia and Tian, 2010; Ding and Bao, 2014). They endure severe stress caused by migration of parents. Data from recent studies show that they are at greater risk for developing mental disorders (He et al., 2012; Wang et al., 2014). In regard to urbanization, studies have demonstrated that being raised in urban area confers a greater risk of psychiatric disorders (Pedersen and Mortensen, 2001; Peen et al., 2010). Previous studies have indicated ethnic minority as a risk factor of PLEs (Morgan et al., 2009). Finally, a few studies have found positive correlation between childhood trauma and PLEs (Jeronimus et al., 2013; Matheson et al., 2013). Our study has two main aims. First, we would like to investigate the prevalence and characteristics of PLEs and depressive and negative experiences among adolescents in Hunan Province, China. Second, some potential genetic and environmental factors associated with more frequent and distressing PLEs were explored in order to provide useful information for mental disorder prevention. Unlike previous studies that usually evaluate childhood traumas in adulthood, our study evaluated the impact of childhood traumas during the period of childhood and adolescence, which may be more relevant. Besides, in order to identify children's distress in the acute aftermath of traumatic events, our study included their impact felt by the children, both at the time of the event and at the survey. 2. Method 2.1. Sample Eleven Middle schools in both Xiangxi Region and Changsha City of Hunan Province were sampled using random cluster method. A total of 5427 students of the first grade from Middle schools were surveyed. All participants and their parent/guardian gave written consent for the study. In general, it took 45 min for the students to fill in the questionnaires. The study was approved by the Ethics Committees of the Second Xiangya Hospital of Central South University. 2.2. Instruments Socio-demographic information to be collected included: gender, age, ethnicity, boarding options, residency status, sources of income, “left-behind” child status, divorced family, parental death, single child status, family history of psychiatric illnesses and past history of any psychiatric conditions for participants. Exclusion criteria for the study include participants with history of any psychiatric conditions and who had N25% of CAPE data missing. We excluded the children with history of psychiatric conditions according to the socio-demographic information in the questionnaires and provided by schools and teachers. The CAPE was used to evaluate the lifetime positive, depressive and negative experiences in the general population (Stefanis et al., 2002; Konings et al., 2006). This self-report instrument consists of 42 items
covering positive, depressive and negative dimensions (PD, DD and ND) on both a frequency scale (1 = never, 2 = sometimes, 3 = often, 4 = nearly always) and a distress scale (1 = not distressed, 2 = a bit distressed, 3 = quite distressed, 4 = very distressed). It includes 20 items of positive psychotic experiences derived from Peters et al. Delusions Inventory (PDI-21) (Peters et al., 1999), 14 items exploring negative experiences derived from an instrument of subjective experience of negative symptoms (SENS) (Selten et al., 1998), and 8 cognitive depressive experiences (Kibel et al., 1993). Previous results have indicated the CAPE to be stable, reliable and valid (Konings et al., 2006). In our study, PLEs were measured through items of PD in the CAPE, while depressive and negative experiences used items of DD and ND, respectively. To assess adolescents' histories of trauma, the Trauma History Questionnaire (THQ) child version (Stover et al., 2010) was used. The scale contains 15 items. Each item was designed to assess the child's history of traumatic events in the lifetime as well as the level of impact on the child, both at the time of the event and at present. Respondents can select a number from “not at all (0)” to “extremely (4)”. Both the Chinese version of CAPE and THQ child version were translated and validated for the first time. Both questionnaires showed good reliability and validity. The papers on the reliability and validity are now under preparation. 2.3. Analyses Analyses were conducted using IBM SPSS Statistics version 19.0. Descriptive statistics were performed for group characteristics. The prevalence was calculated both at the level of “at least sometimes” and “nearly always” respectively in all three dimensions. Frequency of each item was also counted. Correlation analysis was conducted through Pearson's correlation coefficient to investigate associations between frequency scores among the three dimensions, and then between frequency and distress scores. Due to the lack of generally acknowledged cut-off points separately in three dimensions, hierarchical linear cluster analyses were performed on the sample to get high, medium and low score groups. The whole sample was divided into three clusters according to both frequency and distress scores of each dimension, respectively. The same statistical method was also used for the THQ to divide the sample into three groups, respectively according to the level of impact at the time of the event and at present. To investigate the predictors of more frequent and distressing PLEs and depressive and negative experiences, we conducted ordinal logistic regression analyses to calculate odds ratios (ORs) and 95% confidence intervals (95% CI). We entered all dichotomous socio-demographic variables and levels of impact from previous trauma as independent variables, using age as covariate variable. We considered p-value less than 0.05 to be statistically significant. 3. Results 3.1. Description of the sample All 5427 students agreed to participate in our survey. A total of 131 participants who had N25% of CAPE data missing and 23 participants who had history of psychiatric conditions were subsequently removed from further analyses, leaving 5273 with valid data. These participants were aged between 10.0 and 16.6 years, and mean age was 12.6 years (SD = 0.627). Table 1 shows some of the other social-demographic characteristics. 3.2. Characteristics of experiences of three dimensions in the sample Almost all the adolescents in our sample experienced at least one CAPE item during lifetime (entire CAPE = 98.50%, PD (PLEs) = 95.66%, DD = 95.01%, ND = 94.06%). However, prevalence decreased sharply when the frequency increased to “nearly always” (entire
Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
M. Sun et al. / Schizophrenia Research xxx (2015) xxx–xxx Table 1 Descriptive statistics of social-demographic variables*.
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Table 2 Frequency of each item in the three dimensions of the CAPE.
Characteristics
%
Gender (female) Ethnicity (Han) Boarding options (at school) Residency status** (urban) Family has stable income?*** (no) “Left-behind” child status Divorced family Parental death Single child status Family history
48.8 48.7 24.9 34.5 6.6 19.9 4.5 1.3 32.1 3.0
Note: *All the variables are dichotomous. **Residency status represents urban or rural household registration. There is a strict household registration system in China, which divided residents into urban and rural. Rural residents are not able to enjoy the equal social benefits of urban residents, no matter how long they have lived or worked in the cities. ***Stable income means that the family has stable source of income and can support the family members without others' help. On the contrary, not having stable income means that the family needs help from other people or government aid.
CAPE = 26.74%, PD (PLEs) = 17.24%, DD = 7.53%, ND = 15.78%). Frequency of each item shares similar characteristics, but varied in different items (Table 2). Correlations between frequency scores in the three dimensions were positive and significant (p b .01) (Table 3). The positive correlation between frequency and distress scores for entire CAPE was significant and very strong (Fig. 1). The correlation was also very strong for PD (PLEs), DD and ND (r = 0.932, 0.932 and 0.920, p = .000 for all the above) 3.3. Factors associated with more frequent and distressing experiences of three dimensions The sample was divided into high, medium and low score groups respectively in three dimensions (Fig. 2). The groups were confirmed to be significant (p = .000) using the ANOVA method. No reason for potential multicollinearity of all variables was found, with the variance inflation factor (VIF) values of 1.26 and below (O'Brien, 2007). The results are presented in Table 4. In this sample, family history and higher impact from previous trauma at present predicted more frequent and distressing experiences of all three dimensions. Adolescents with urban household registration had more frequent and distressing PLEs and depressive experiences than their rural counterparts, while females and “left-behind” children had more frequent and distressing depressive and negative experiences. In addition, adolescents who had parental death experienced more frequent and distressing depressive experiences only. As impact from previous trauma at present showed high ORs in all three dimensions, further analysis of covariance was conducted between clusters of trauma impact and frequency scores of each CAPE dimension, using age as covariance (Table 5). In comparison between the two groups, symptoms from all three dimensions associated with medium trauma impact are significantly higher than low trauma impact (p b .05). However, there is no significant difference between medium and high trauma impact, which may be explained by the small sample size of the high trauma impact group. 4. Discussion A median prevalence of 17% (range from 5% to 35.3%) was reported in a recent review on PLEs (Kelleher et al., 2012). Only items on auditory hallucinations were chosen for the analysis in Kelleher et al.'s review, while our study examined a broader range of symptoms. It can explain why the prevalence in our study was much higher. However, when we examined items related to auditory hallucinations in our sample, the prevalence of the question “Do you ever hear voices when you are
Never (%)
At least sometimes (%)
Nearly always (%)
Positive dimension (PLEs) 2. Double meaning 5. Messages from magazines or TV 6. False appearance 7. Being persecuted 10. Conspiracy 11. Being important 13. Being special 15. Telepathy 17. Influenced by devices 20. Voodoo 22. Odd looks 24. Thought withdrawal 26. Thought insertion 28. Thought broadcasting 30. Thought echo 31. External control 33. Verbal hallucinations 34. Voices conversing 41. Capgras 42. Visual hallucinations
42.8 75.2 36.9 70.5 69.9 42.0 63.3 46.0 53.1 72.1 59.8 80.6 76.1 70.6 49.0 77.8 63.1 76.5 79.7 80.6
57.2 24.8 63.1 29.5 30.1 58.0 36.7 54.0 46.9 27.9 40.2 19.4 23.9 29.4 51.0 22.2 36.9 23.5 20.3 19.4
0.7 0.5 2.6 0.6 0.9 4.5 3.5 3.5 3.5 2.8 1.8 0.5 0.8 1.4 2.5 1.1 1.6 0.9 1.2 0.6
Depressive dimension 1. Sad 9. Pessimism 12. No future 14. Not worth living 19. Frequently cry 38. Guilty 39. Failure 40. Feeling tense
18.9 53.4 79.6 78.7 74.9 40.8 63.1 21.1
81.1 46.6 20.4 21.3 25.1 59.2 36.9 78.9
0.7 1.3 1.1 3.5 1.2 1.3 1.5 3.7
Negative dimension 3. Lack of enthusiasm 4. Not talkative 8. No emotion 16. No interest in others 18. No motivation 21. No energy 23. Empty mind 25. Lack of activity 27. Blunted feelings 29. Lack of spontaneity 32. Blunted emotions 35. Lack of hygiene 36. Unable to terminate 37. Lack of hobby
51.5 46.1 50.2 72.3 43.8 66.2 57.2 47.6 69.2 50.2 68.3 71.5 73.6 76.4
48.5 43.9 49.8 27.7 56.2 33.8 42.8 52.4 30.8 49.8 31.7 28.5 26.4 23.6
3.9 3.1 1.6 1.2 2.9 1.3 0.8 2.4 1.0 2.4 1.1 0.9 0.9 2.7
Note: CAPE, the Community Assessment of Psychic Experiences; PLEs, psychotic-like experiences.
alone” with a frequency of “at least “sometimes”, is 36.9%. This is compatible with the findings in the studies used in this meta-analysis. However, PLEs are common in adolescents, with a small proportion having frequent PLEs, which suggest that transient PLEs are not pathological. Therefore the focus of our study was the risk factors associated with more frequent and distressing PLEs. Our results showed more PLEs in adolescents with urban household registration, although they enjoyed more social benefits. Similarly, there is a higher prevalence of psychotic disorders in urban areas versus rural Table 3 Correlations between dimensions of the CAPE frequency scale.
PD (PLEs) DD ND CAPE total
PD (PLEs)
DD
ND
CAPE total
1 0.670** 0.614** 0.906**
1 0.710** 0.852**
1 0.869**
1
Note: ** p b .01. CAPE, the Community Assessment of Psychic Experiences; PD, positive dimension; PLEs, psychotic-like experiences; DD, depressive dimension; ND, negative dimension.
Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
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Fig. 1. Relationship between frequency and distress scores for entire CAPE (r = 0.934, p = .000). CAPE, the Community Assessment of Psychic Experiences questionnaire.
Table 4 Logistic regression of predictors of more frequent and distressing experiences of three dimensions. Model PD (PLEs)
Gender Ethnicity Boarding options Residency status Stable income “Left-behind” child status Divorced family Parental death Single child Family history THQ1 THQ2
Model DD
Model ND
OR
(95%CI)
OR
(95%CI)
OR
(95%CI)
1.03 1.47 0.61 2.32** 1.08 1.45 1.63 2.62 0.96 2.62* 0.57 8.44***
(0.63, 1.69) (0.87, 2.49) (0.31, 1.19) (1.36, 3.96) (0.41, 2.83) (0.78, 2.72) (0.64, 4.19) (0.77, 8.96) (0.55, 1.69) (1.06, 6.46) (0.11, 2.98) (4.60, 15.50)
1.81** 0.95 1.02 1.55* 1.35 1.65* 1.18 2.73* 1.32 2.13* 1.05 4.92***
(1.24, 2.64) (0.63, 1.39) (0.68, 1.54) (1.04, 2.31) (0.73, 2.48) (1.08, 2.52) (0.54, 2.55) (1.09, 6.82) (0.87, 2.01) (1.04, 4.33) (0.30, 3.67) (2.84, 8.54)
1.49** 1.14 1.06 1.20 1.33 2.00*** 1.11 1.78 1.05 1.81* 1.48 3.31***
(1.16, 1.91) (0.89, 1.48) (0.81, 1.40) (0.91, 1.58) (0.88, 2.01) (1.52, 2.63) (0.63, 1.96) (0.82, 3.88) (0.79, 1.40) (1.09, 3.01) (0.61, 3.60) (2.14, 5.13)
Note: *p b .05, **p b .01, ***p b .001. PD, positive dimension; PLEs, psychotic-like experiences; DD, depressive dimension; ND, negative dimension; CI, confidence intervals; OR, odds ratio; THQ1 represents impact from trauma at the time of the event; THQ2 impact from trauma at present. Adjusted for age.
areas in some previous studies (Faris and Dunham, 1939; Mortensen et al., 1999; Peen et al., 2010). Epidemiologic research has documented the associations that particular features of the urban environment, such as concentrated disadvantage (i.e., areas characterized by high poverty, unemployment, and other socio-economical disadvantages), residential segregation, social disorganization, and less green space, contribute to the risk of psychotic disorders (Faris and Dunham, 1939; Galea et al., 2011; McKenzie et al., 2013). Recent studies attempting to explore the mechanism between urban areas and psychotic disorders, found that urban upbringing could impact brain architecture (Haddad et al., 2014), change the (re)activity of the HPA axis (Steinheuser et al., 2014), or make changes in DNA methylation (Galea et al., 2011). Although the exact mechanisms are unknown, harmful influence of urban environment may start as early as growing stage according to our study. It is well-known that having a family history of psychiatric illness is associated with elevated risk for developing psychotic disorders (Mortensen et al., 1999). Studies on monozygotic and dizygotic twins have also demonstrated that genetic contribution was apparent for self-reported PLEs in the general population (Lataster et al., 2009; Wigman et al., 2011). In our study we found individuals with family history tended to have more frequent and distressing PLEs. Therefore we
speculate that genetic influence may play an important role in aggravating severity of PLEs. A recent meta-analysis reported a medium to large effect of childhood adversity in people with psychosis (Matheson et al., 2013). However, there was no significant relation between PLEs and impact from trauma at the time of the event in our study, whereas adolescents who had more impact from previous trauma at present had a much higher risk of PLEs. Therefore we can infer that different changes have taken place in these adolescents after the trauma. As we have known, people's responses to trauma vary widely. Some develop mental Table 5 Comparison among different trauma impact groups at present on frequency scores of each dimension (mean ± SD).
PD (PLEs) DD ND
Low score group
Medium score group
High score group
p
28.55 ± 6.459 12.25 ± 2.938 20.77 ± 5.045
37.16 ± 8.995 15.63 ± 4.429 24.95 ± 6.685
35.22 ± 6.671 16.05 ± 2.162 21.91 ± 2.206
b.001 b.001 b.001
Note: SD, standard deviation; PD, positive dimension; PLEs, psychotic-like experiences; DD, depressive dimension; ND, negative dimension. Adjusted for age.
Please cite this article as: Sun, M., et al., Psychotic-like experiences and associated socio-demographic factors among adolescents in China, Schizophr. Res. (2015), http://dx.doi.org/10.1016/j.schres.2015.05.031
M. Sun et al. / Schizophrenia Research xxx (2015) xxx–xxx
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Fig. 2. Results of cluster analyses in three dimensions. PD, positive dimension (or psychotic-like experiences); DD, depressive dimension; ND, negative dimension.
disorders or mild to moderate psychological symptoms that resolve rapidly, and others report no new psychological symptoms (Southwick and Charney, 2012). The different responses depend on different processes of adaptation in face of traumas, which can be called resilience. So it is not traumas themselves but the poor resilience of the subjects that leads directly to higher level of impact at present and results in more frequent and distressing PLEs finally. Resilience depends on numerous emotion regulation, social, physical health, cognitive factor, neurobiological risk and protective factors. Therefore early age cognitive behavioral therapy interventions, and measures on improving emotion regulation (i.e., delay gratification and frustration education) and physical health may be beneficial to prevention of psychotic disorders. However, there was no significant relation between PLEs and ethnicity in our study, which was thought to be a risk factor. Ethnic minority status is considered to be a risk factor of psychotic disorders, which may be explained by discrimination and rejection sensitivity (Anglin et al., 2014; Berg et al., 2014). The different result in our study may be partly interpreted as the result of policy for the protection of minorities in China. Most of the minority we investigated lived in the minority compact-communities, with no long-term experience of exclusion. “Left-behind” children, as a unique social phenomenon in contemporary China, have attracted increasing attention. Previous research found the “left-behind” children have lower self-concept and more mental health problems (He et al., 2012; Wang et al., 2014). However, no higher risk for PLEs, but depressive and negative experiences was found in our study. Loneliness (Jia and Tian, 2010), high risk for suffering abuse and bullying in schools caused by lack of care (Givaudan and Pick, 2013), may give rise to the frequent and severe depressive experiences. Lack of adequate family bonding, and enough time for school activities may cause lack of necessary mental stimulation in the critical period of brain development, which may result in more negative experiences. However, follow-up study is needed to find the internal relation between development of psychoses and “left-behind” children. In summary, similar to psychotic disorders, more frequent and distressing PLEs are probably associated with genetic factors as well as environmental factors, which are consistent with the continuity model of PLEs. The dimensional representation of the psychosis phenotype suggests that psychosis is the simultaneous variation of correlated symptom dimensions. However, this distribution of psychosis can extend into general population as well, which is proved in our study. The subclinical depressive and negative experiences also shared similar risk factors with the corresponding symptoms at the clinical level, which may further prove the continuum of psychosis in dimensional approach. In our study, there are also many overlapping risk factors in three dimensions, which can also be found between affective and non-affective psychotic syndromes. So it is attractive to speculate from the subclinical level that etiologic relation exists between different symptom dimensions of psychosis.
There are some limitations for the study. First, as self-reported questionnaires were used, and participants were very young, it is possible that some of the questionnaires were not carefully completed. So the findings of our study have to be interpreted with caution. Second, there were no strict exclusion criteria for participants who had history of psychiatric conditions, as we did not adopt structured instrument for making diagnoses. Third, family history of psychiatric illnesses is not necessarily due to genetic etiology as it can also be related to a shared environment, or other reasons. It may be helpful to improve the global mental health if we can identify adolescents with high-risk PLEs, and provide support or interventions for them from an early stage. However, further prospective studies are required to examine if PLEs in adolescence are associated with a higher risk to develop psychoses in adulthood, and we are planning to follow up our cohort of subjects prospectively to address this question. Role of funding source The work was supported by the National Natural Science Foundation of China (81271485, 81471362 to Z.N. Liu) and the Hunan Provincial Natural Science Foundation of China (07JJ3046 to Z.M. Xue). Contributors Authors Meng Sun, Xinran Hu, Wen Zhang and Zhening Liu designed the study and wrote the protocol. All authors participated in data collection. Authors Meng Sun and Jingcheng Shi undertook the statistical analysis, and author Meng Sun wrote the first draft of the manuscript. Authors Helen Chiu and Zhening Liu modified the manuscript. All authors contributed to and have approved the final manuscript. Conflict of interest None. Acknowledgments The authors would like to thank Dr. Eric Chen and Dr. Sherry Kit wa Chan from the University of Hong Kong. Both of them offered advice on the study design.
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