Lifetime Prevalence and Correlates of Schizophrenia-Spectrum, Affective, and Other Non-affective Psychotic Disorders in the Chinese Adult Population

Abstract

Lifetime prevalence of psychotic disorders varies widely across studies. Epidemiological surveys have rarely examined prevalences of specific psychotic disorders other than schizophrenia, and the majority used a single-phase design without employing clinical reappraisal interview for diagnostic verification. The current study investigated lifetime prevalence, correlates and service utilization of schizophrenia-spectrum, affective, and other non-affective psychotic disorders in a representative sample of community-dwelling Chinese adult population aged 16–75 years (N = 5719) based on a territory-wide, population-based household survey for mental disorders in Hong Kong. The survey adopted a 2-phase design comprising first-phase psychosis screening and second-phase diagnostic verification incorporating clinical information from psychiatrist-administered semi-structured interview and medical record review to ascertain DSM-IV lifetime diagnosis for psychotic disorders. Data on sociodemographics, psychosocial characteristics and service utilization were collected. Our results showed that lifetime prevalence was 2.47% for psychotic disorder overall, 1.25% for schizophrenia, 0.15% for delusional disorder, 0.38% for psychotic disorder not otherwise specified, 0.31% for bipolar disorder with psychosis, and 0.33% for depressive disorder with psychosis. Schizophrenia-spectrum disorder was associated with family history of psychosis, cigarette smoking and variables indicating socioeconomic disadvantage. Victimization experiences were significantly related to affective psychoses and other non-affective psychoses. Around 80% of participants with any psychotic disorder sought some kind of professional help for mental health problems in the past year. Using comprehensive diagnostic assessment involving interview and record data, our results indicate that approximately 2.5% of Chinese adult population had lifetime psychotic disorder which represents a major public health concern.

Introduction

Psychotic disorders represent a group of severe mental disorders that constitutes one of the leading causes of disability worldwide.¹ People with psychotic disorders experience significant functional impairment and are at markedly elevated risk of suicide,² physical morbidity and premature mortality.^3,4 The disorders incur substantial socioeconomic cost through direct healthcare spending and indirect costs such as loss of productivity and caregiver burden. They represent a major public health challenge, and are associated with a considerable degree of unmet therapeutic need.

Prevalence data are essential for disease burden estimation, service planning and aetiological investigation. Lifetime prevalence estimates of psychotic disorders vary widely across population-based surveys.^5–7 Most previous research has focused on schizophrenia. Two recent reviews reported median lifetime prevalence of schizophrenia of 0.4% and 0.48%, respectively.^6,7 A number of studies examined lifetime prevalence of more broadly-defined non-affective psychosis (NAP), with a range between 0.5% and 2.3%.^8–14 Such divergence in prevalence rates may reflect true differences between geographic areas. It may also be attributable to methodological variation in survey design, sampling frame and strategy, as well as diagnostic procedures and criteria for case identification. In particular, prevalence estimates of psychosis in the community samples are strongly influenced by methods of assessment and diagnostic assignment. The majority of prior epidemiological surveys have adopted a single-phase design and relied on lay-administered fully-structured interviews to derive a diagnosis of psychotic disorders.^6,7 Evidence has, nonetheless, demonstrated that diagnoses of psychotic disorders generated by lay-administered structured interviews are not well concordant with those ascertained by clinical reappraisal interviews conducted by psychiatrists.^9,10,12 Very few population-based studies have used additional sources of information such as medical records to supplement interviews for diagnostic verification.¹² Significant discrepancy in methodology and estimated prevalence precludes generalizability of findings to other communities. There is a paucity of data on prevalence of affective psychoses and specific psychotic disorders other than schizophrenia.

In this article, we present lifetime prevalences, sociodemographic and psychosocial correlates, and service utilization patterns of schizophrenia-spectrum, affective, and other non-affective psychotic disorders in a representative sample of the Chinese adult population in Hong Kong based on the Hong Kong Mental Morbidity Survey (HKMMS),¹⁵ which is the first territory-wide, population-based, face-to-face household survey for mental disorders in Hong Kong. The survey employed a 2-phase approach comprising first-phase psychosis screening and second-phase diagnostic verification incorporating clinical information from psychiatrist-administered semi-structured interview and medical record review so as to provide a more accurate estimation of lifetime prevalences of psychotic disorders.

Methods

Survey Design and Sample

The HKMMS is based on a representative, noninstitutionalized sample of the Hong Kong Chinese adult population. Hong Kong is a metropolitan city located at the southeastern tip of China. It has a population of approximately 7.24 million with ethnic Chinese comprising 91% of the population.¹⁶ The city covers an area of about 1100 km² and is one of the most densely populated territories in the world (with average population density of 6690 persons/km²).

The survey adopted a multistage stratified cluster sampling procedure. The sampling frame consisted of randomly selected addresses provided by the Census and Statistics Department of Hong Kong Government, and were stratified according to geographical districts and the nature of premises (private/public housing). One adult aged 16–75 years was interviewed in each eligible household. This survey was restricted to community-dwelling adult population and did not examine people who were homeless, institutionalized (mental hospitals or residential homes) or in prison.

The study employed a 2-phase design, taking reference to the UK Adult Psychiatric Morbidity Survey.^17,18 The phase 1 interview, which was administered by nonclinically trained research staff, comprised assessments on nonpsychotic mental disorders, alcohol and substance use, suicidal behaviors, and screening for possible psychosis. The interview also included questionnaires examining sociodemographics, health service utilization and risk factors for mental disorders. A total of 5719 respondents completed phase 1 interviews. The participation rate was 68%. A subsample of respondents (n = 312, 5.5% of the survey sample) who screened positive for psychosis in phase 1 were selected for a second phase aimed to provide a definitive ascertainment of psychotic disorder on the basis of clinician-administered diagnostic interview (Chinese-bilingual Structured Clinical Interview for DSM-IV, CB-SCID-I/P¹⁹) and medical record review. Two hundred thirty-two participants underwent second-phase diagnostic assessment (response rate: 74.4%). Of these, 94 (30.1%) were evaluated with both CB-SCID-I/P and medical record review, while 48 (15.4%) and 90 (28.8%) had only CB-SCID-I/P ratings and medical record data, respectively. To ascertain specificity of psychosis screen, 2% of the respondents (n = 110) who screened negative for psychosis in phase 1 were randomly selected to attend clinician-administered diagnostic interviews, with none having received lifetime diagnosis of any psychotic disorder (supplementary figure S1). Details of the survey method and findings regarding common mental disorders have been reported elsewhere.^15,20 Fieldwork took place between November 2010 and May 2013. The study was approved by research ethics committees of the Chinese University of Hong Kong, the University of Hong Kong and the Hospital Authority. All participants provided written informed consent in each phase of the survey.

Identification of Psychotic Disorders

In phase 1, the Psychosis Screening Questionnaire (PSQ),²¹ which comprises 5 probes and 5 secondary questions enquiring about mania, thought interference, paranoia, strange experiences and hallucinations, was administered to screen for psychotic symptoms in the past 12 months. Supplementary enquiry for occurrence of these psychotic symptoms beyond the past year was also conducted to capture lifetime presence of possible psychosis. Respondents were invited for phase 2 assessment if they met one or more of the 5 following psychosis screening criteria: a self-reported diagnosis of psychotic disorder; past or current treatment with antipsychotic medication; a history of psychiatric inpatient treatment; endorsement of one or more of the 5 items in the PSQ; and endorsement of occurrence of psychotic symptoms in supplementary enquiry.

In phase 2, clinical diagnostic interviews and/or medical record reviews were conducted to verify lifetime diagnosis of psychotic disorder. The CB-SCID-I/P,¹⁹ a semi-structured interview providing DSM-IV²² diagnoses of psychotic disorders, was administered by qualified psychiatrists within 2 months following completion of the phase 1 assessment. A previous validation study showed that CB-SCID-I/P yielded reliable DSM-IV diagnoses in Chinese patients with psychotic disorders.¹⁹ Twenty-three psychiatrists, all with at least 5 years of clinical experience in treating mental disorders, conducted the diagnostic interviews. They completed intensive training on the use of CB-SCID-I/P and achieved satisfactory diagnostic concordance (κ = 0.75) prior to study commencement. All the CB-SCID-I/P ratings were reviewed by a senior research psychiatrist (L.L.C.W. or C.W.C.). Weekly research meetings were held throughout the study period to ensure strict adherence to the assessment protocol and to resolve discrepancies in diagnostic ratings between senior research psychiatrists and interviewers. In cases where clinical information was ambiguous, participants were re-contacted for clarification.

Participants’ medical records were retrieved from the computerized Clinical Management System (CMS)²³ of the Hospital Authority for diagnostic verification, excluding those who refused consent to record review or had no prior contact with public healthcare system which is the major mental health service provider in Hong Kong for patients with severe mental disorder. The Hospital Authority manages all public hospitals, specialist and general outpatient clinics covering the whole territory of Hong Kong. The CMS is a centralized medical database comprising integrated, longitudinal electronic health records of all patients treated in public healthcare system across all service settings. Clinical information of CMS is directly recorded by clinicians and other healthcare professionals. In this study, medical notes were retrieved detailing inpatient, day-patient and outpatient psychiatric treatments, and prescription records of participants since their first contact with public mental health services. A clinical summary of each participant was compiled by a senior research staff member (W.C.S.M.), who systematically extracted cumulative lifetime clinical data from medical records using standardized data documentation form. The summary was scrutinized by a senior research psychiatrist (C.W.C.).

The final best-estimate lifetime DSM-IV diagnoses were determined by 2 senior research psychiatrists (L.L.C.W. and C.W.C.) in consensus diagnostic review meetings taking into consideration all available information including CB-SCID-I/P ratings and/or clinical summaries extracted from medical records. In this report, DSM-IV diagnoses for any psychotic disorder included schizophrenia, schizoaffective disorder, schizophreniform disorder, brief psychotic disorder, delusional disorder, psychotic disorder not otherwise specified (NOS), bipolar disorder (BP) with psychotic features and major depressive disorder (MDD) with psychotic features. Substance-induced psychosis and psychotic disorder due to general medical condition were excluded.

Assessment of Correlates and Service Utilization

Sociodemographic assessments included age, sex, educational level, marital status, employment status, personal income and housing type. Data on family history of psychotic disorders and current smoking status were obtained. Alcohol consumption in the past year was assessed using Alcohol Use Disorders Identification Test²⁴ with total score ≥8 indicating harmful drinking. A questionnaire was administered to obtain information on illicit substance use in the past year covering opiates, cannabis, ketamine, ecstasy, amphetamines, cocaine, tranquillizers, volatile substances, and hallucinogens. Lifetime exposure to potentially traumatic life events was evaluated using Life Event Checklist.²⁵ To explore the relationship between victimization experience and psychosis, victimization was operationalized as the experience of any of the following lifetime traumatic life events: physical assault, assault with a weapon, sexual assault, other unwanted sexual experience or captivity. Information on health service utilization for mental health problems in the past year was also obtained.

Analytic Strategy

Lifetime prevalence estimates for psychotic disorders were computed by applying weightings in 2 steps. First, post-stratification weights were assigned on the basis of age, sex and housing type distributions using data from 2011 Hong Kong Population Census²⁶ to assure the representativeness of the survey sample with respect to the total Hong Kong Chinese adult population. Second, weights were calculated as the inverse of the probability of response for nonresponse adjustment. Weighted prevalences were derived using a bootstrap resampling method, which generated SE from 1000 bootstrap replications with random replacement to account for the effects of stratification and clustering on variance estimates, and were presented as percentages with 95% CI, stratified by sex and age groups (16–30, 31–45, 46–60, and 61–75 years). Sex difference in prevalence of psychotic disorders was examined using chi-square test. To determine sociodemographic and psychosocial correlates of psychotic disorders, a series of univariate logistic regression analyses were conducted. Those variables that showed significant associations (P < .05) in preceding analyses were then included in multivariate regression models. ORs and 95% CIs were derived from regression models. Patterns of health service utilization in the past year were reported as proportions (%) with SE. Analyses of correlates and service utilization were conducted separately on the following broadly-defined diagnostic categories: any psychotic disorder, schizophrenia-spectrum disorder (schizophrenia, schizoaffective disorder and schizophreniform disorder), other non-affective psychoses (other NAP) (delusional disorder, brief psychotic disorder and psychotic disorder NOS), and affective psychoses (BP with psychotic features and MDD with psychotic features). The level of statistical significance was set at P < .05. All analyses were performed with STATA version 12.0 (StataCorp).

Results

Prevalence Estimates of Psychotic Disorders

Table 1 shows lifetime prevalence estimates of broadly-defined and specific diagnostic categories of psychotic disorders by sex. Lifetime prevalences of broadly-defined categories by sex and age groups are presented in table 2. Lifetime prevalence was 2.47% (95% CI: 1.99%–2.96%) for any psychotic disorder, 2.17% (95% CI: 1.39%–2.95%) for NAP (including schizophrenia-spectrum disorder and other NAP), 1.30% (95% CI: 0.94%–1.66%) for schizophrenia-spectrum disorder, 0.53% (95%CI: 0.33%–0.74%) for other NAP, and 0.64% (95% CI: 0.38%–0.90%) for affective psychoses. Of specific psychotic disorders, lifetime prevalence was highest for schizophrenia (1.25%, 95%CI: 0.90%–1.61%), followed by psychotic disorder NOS (0.38%, 95% CI: 0.20%–0.55%), MDD with psychotic features (0.33%, 95% CI: 0.14%–0.52%), BP with psychotic features (0.31%, 95% CI: 0.13%–0.50%), and delusional disorder (0.15%, 95% CI: 0.05%–0.26%). Only 1 and 3 participants received a lifetime diagnosis of schizophreniform disorder and schizoaffective disorder, respectively. None had brief psychotic disorder. There was no sex difference in lifetime prevalence of any broadly-defined and specific diagnostic categories of psychosis (all Ps > .05).

Table 1.

Lifetime Prevalences of DSM-IV Psychotic Disorders

Diagnosis	No. of Participantsa	Prevalence, % (95% CI)b,c
		Men	Women	Total
Any psychotic disorder	130	2.12 (1.52–2.71)	2.69 (2.00–3.37)	2.47 (1.99–2.96)
Non-affective psychosisd	100	2.60 (0.76–4.43)	1.91 (1.34–2.48)	2.17 (1.39–2.95)
Schizophrenia-spectrum disorder	67	1.24 (0.78–1.70)	1.34 (0.84–1.84)	1.30 (0.94–1.66)
Schizophrenia	63	1.19 (0.74–1.65)	1.29 (0.80–1.78)	1.25 (0.90–1.61)
Schizoaffective disordere	3	—	—	—
Schizophreniform disorderf	1	—	—	—
Other non-affective psychoses	33	0.47 (0.20–0.74)	0.57 (0.29–0.85)	0.53 (0.33–0.74)
Delusional disorder	11	0.26 (0.05–0.47)	0.09 (0.00–0.20)	0.15 (0.05–0.26)
Psychotic disorder NOS	22	0.21 (0.03–0.39)	0.48 (0.22–0.74)	0.38 (0.20–0.55)
Affective psychoses	30	0.41 (0.14–0.68)	0.78 (0.39–1.17)	0.64 (0.38–0.90)
BP with psychotic features	15	0.26 (0.05–0.47)	0.35 (0.08–0.61)	0.31 (0.13–0.50)
MDD with psychotic features	15	0.15 (0.00–0.32)	0.43 (0.14–0.72)	0.33 (0.14–0.52)

Note: BP, bipolar disorder; MDD, major depressive disorder; NOS, not otherwise specified.

^aCrude number of psychotic disorder.

^bWeighted prevalence estimates were computed to adjust the data to the 2011 Hong Kong Population Census on the basis of age, sex and housing type distributions, and for nonresponse in phase 2 assessment.

^cThere was no significant sex difference in lifetime prevalence in each of the diagnostic categories for psychotic disorders (all Ps > .05).

^dNon-affective psychosis included schizophrenia-spectrum disorder and other non-affective psychoses.

^eOne man and 2 women were diagnosed to have schizoaffective disorder. Prevalence rates were not reported as the number of cases was too few to provide reliable estimates.

^fOne man was diagnosed to have schizophreniform disorder. Prevalence rates were not reported as the number of cases was too few to provide reliable estimates.

Table 2.

Lifetime Prevalences of DSM-IV Psychotic Disorders by Age Groups and Sex

	Prevalence by Age Group, % (95% CI)a
Diagnosis	16–30 Years	31–45 Years	46–60 Years	61–75 Years
All participants
Any psychotic disorder	1.46 (0.61–2.32)	2.64 (1.73–3.55)	2.73 (1.90–3.57)	2.49 (1.39–3.59)
Non-affective psychosisb	0.70 (0.14–1.26)	2.05 (1.25–2.85)	2.02 (1.32–2.71)	2.13 (1.12–3.15)
Schizophrenia-spectrum disorderc	0.38 (0.00–0.78)	1.68 (0.92–2.43)	1.39 (0.80–1.98)	1.17 (0.48–1.86)
Other non-affective psychosesd	0.32 (0.00–0.71)	0.37 (0.09–0.66)	0.62 (0.25–1.00)	0.96 (0.21–1.71)
Affective psychosese	0.76 (0.11–1.41)	0.59 (0.16–1.02)	0.72 (0.24–1.20)	0.36 (0.00–0.79)
Men
Any psychotic disorder	0.65 (0.01–1.29)	3.30 (1.81–4.80)	1.81 (0.95–2.67)	2.44 (0.96–3.93)
Non-affective psychosis	0.46 (0.00–0.99)	2.39 (1.10–3.68)	1.66 (0.82–2.49)	2.05 (0.77–3.34)
Schizophrenia-spectrum disorder	0.32 (0.00–0.78)	1.65 (0.58–2.72)	1.29 (0.55–2.03)	1.42 (0.29–2.54)
Other non-affective psychoses	0.14 (0.00–0.41)	0.74 (0.01–1.47)	0.37 (0.00–0.74)	0.64 (0.01–1.27)
Affective psychoses	0.19 (0.00–0.55)	0.91 (0.14–1.68)	0.16 (0.00–0.38)	0.39 (0.00–1.15)
Women
Any psychotic disorder	2.06 (0.66–3.47)	2.32 (1.19–3.46)	3.28 (2.05–4.52)	2.53 (0.94–4.11)
Non-affective psychosis	0.88 (0.00–1.76)	1.89 (0.87–2.90)	2.23 (1.24–3.22)	2.19 (0.68–3.71)
Schizophrenia-spectrum disorder	0.42 (0.00–1.04)	1.69 (0.70–2.68)	1.45 (0.62–2.28)	0.97 (0.11–1.84)
Other non-affective psychoses	0.45 (0.00–1.09)	0.20 (0.00–0.43)	0.78 (0.23–1.33)	1.22 (0.01–2.48)
Affective psychoses	1.19 (0.09–2.29)	0.44 (0.01–0.96)	1.05 (0.30–1.81)	0.33 (0.00–0.81)

Note: NOS, not otherwise specified.

^aWeighted prevalence estimates were computed to adjust the data to the 2011 Hong Kong Population Census on the basis of age, sex and housing type distributions, and for nonresponse in phase 2 assessment.

^bNon-affective psychosis included schizophrenia-spectrum disorder and other non-affective psychoses.

^cSchizophrenia-spectrum disorder included schizophrenia, schizoaffective disorder and schizophreniform disorder.

^dOther non-affective psychoses included delusional disorder and psychotic disorder NOS.

^eAffective psychoses included bipolar disorder with psychotic features and major depressive disorder with psychotic features.

Sociodemographic and Psychosocial Correlates of Psychotic Disorders

Supplementary table S1 and table 3 summarize the results on the associations of psychotic disorders with sociodemographic and psychosocial variables in univariate and multivariate analyses, respectively. Participants with any psychotic disorder were significantly more likely to be within the 3 older age strata (compared to the reference age group of 16–30 years), single or divorced/separated, unemployed, a current smoker, to have lower personal income (below HKD 6000 per month), a family history of psychotic disorder and experience of victimization. Schizophrenia-spectrum disorder was associated with the 3 older age groups, single or divorced/separated marital status, unemployment, low personal income, current smoker status and a family history of psychotic disorder. Being economically inactive was associated with a decreased odds ratio for schizophrenia-spectrum disorder. Other NAP was associated with substance use in the past year and victimization experience. Divorced/separated marital status, unemployment, a family history of psychotic disorder and victimization experience were associated with an increased probability of affective psychoses.

Table 3.

Sociodemographic and Psychosocial Correlates of Lifetime DSM-IV Psychotic Disorders in Multivariate Models^a

	Any Psychotic Disorder		SS Disorder		Other NAP		Affective Psychoses
Variables	OR (95% CI)	P	OR (95% CI)	P	OR (95% CI)	P	OR (95% CI)	P
Age
16–30	Ref		Ref		—		—
31–45	4.92 (2.44–9.95)	<.001 ***	9.70 (3.15–29.82)	<.001 ***	—		—
46–60	3.67 (1.76–7.66)	.0 01 **	7.54 (2.35–24.14)	.001 **	—		—
61–75	3.22 (1.36–7.59)	.008 **	9.08 (2.39–34.48)	.001 **	—		—
Educational level
Primary level or below	Ref		Ref		Ref		—
Lower secondary level	0.62 (0.35–1.12)	.117	0.52 (0.23–1.20)	.126	0.60 (0.23–1.55)	.294	—
Upper secondary level	0.70 (0.40–1.23)	.212	0.64 (0.29–1.38)	.251	0.38 (0.09–0.92)	.058	—
Post-secondary level	0.67 (0.29–1.56)	.353	0.62 (0.19–2.00)	.420	0.46 (0.10–2.09)	.315	—
Marital status
Married or cohabited	Ref		Ref		Ref		Ref
Never married	4.96 (2.97–8.26)	<.001 ***	8.07 (4.01–16.27)	<.001 ***	2.01 (0.76–5.36)	.162	2.52 (1.00–6.37)	.050
Divorced or separated	2.62 (1.57–4.38)	<.001 ***	2.48 (1.15–5.35)	.020 *	2.09 (0.86–5.13)	.106	2.98 (1.13–7.87)	.028*
Employment status
Working	Ref		Ref		Ref		Ref
Economically inactiveb	0.58 (0.31–1.08)	.084	0.27 (0.10–0.74)	.010 *	0.84 (0.29–2.37)	.737	0.83 (0.28–2.45)	.730
Unemployed	3.02 (1.78–5.15)	<.001 ***	2.63 (1.28–5.42)	.009 **	2.78 (0.99–7.79)	.052	3.00 (1.05–8.58)	.041 *
Personal income per month (HKD)c					Ref
Below 6,000	Ref		Ref		Ref		Ref
6000–9999	0.54 (0.31–0.95)	.032 *	0.29 (0.12–0.71)	.006 **	1.09 (0.43–2.78)	.848	0.83 (0.30–2.32)	.725
10 000–19 999	0.34 (0.17–0.66)	.001 **	0.28 (0.11–0.71)	.007 **	0.38 (0.09–1.53)	.172	0.51 (0.14–1.84)	.304
Above 20 000	0.07 (0.02–0.25)	<.001 ***	0.03 (0.00–0.29)	.002 **	0.18 (0.02–1.74)	.139	0.15 (0.02–1.33)	.088
Type of housing
Private housing	Ref		Ref		Ref		Ref
Public housing	1.34 (0.87–2.05)	.182	1.42 (0.78–2.59)	.257	1.13 (0.50–2.52)	.770	1.18 (0.54–2.62)	.675
Family history of psychotic disorder
No	Ref		Ref		—		Ref
Yes	3.87 (2.01–7.44)	<.001 ***	4.77 (2.12–10.75)	<.001 ***	—		4.66 (1.55–14.00)	.006 **
Current smoker
No	Ref		Ref		Ref		—
Yes	1.65 (1.03–2.66)	.037 *	2.19 (1.18–4.06)	.013 *	1.38 (0.56–3.43)	.488	—
Substance use in past year
No	Ref		—		Ref		—
Yes	2.74 (0.78–9.67)	.116	—		7.13 (1.41–35.95)	.017 *	—
Lifetime victimization experience
No	Ref		Ref		Ref		Ref
Yes	2.15 (1.40–3.29)	<.001 ***	1.22 (0.65–2.31)	.536	2.64 (1.20–5.81)	.016 *	4.33 (2.03–9.22)	<.001***

Note: NAP, non-affective psychoses; SS, schizophrenia-spectrum.

^aMultivariate regression analyses were conducted with adjusted odds ratios presented.

^bEconomically inactive included retired, homemaker and student.

^cPersonal income by quartile based on the 2011 Hong Kong Population Census; HKD 1 = USD 7.8.

*P < .05, **P < .01, ***P < .001.

Service Utilization

As shown in table 4, 79.8% of participants with any psychotic disorder had obtained some kind of professional help for mental health problems in the past year, and approximately 3-quarters had mental health specialty treatment (75.9%) and psychiatrist consultation (74.4%). Very few sought help from general medical health providers (2.3%) or traditional Chinese medical practitioners (0.8%), while 22.5% contacted social services. The proportion receiving any health service and mental health specialty treatment was significantly higher for schizophrenia-spectrum disorder and affective psychoses than for other NAP.

Table 4.

Twelve-month Health Service Utilization for Mental Health Problems in Participants with DSM-IV Psychotic Disorders

Types of Health Professionals	Any Psychotic Disorder (n = 130)	SS Disorder (n = 67)	Other NAP (n = 33)	Affective Psychoses (n = 30)	Group Differencesa
	% (SE)	% (SE)	% (SE)	% (SE)
Mental health specialty sector	75.97 (3.78)	86.57 (4.20)	46.88 (8.96)	83.33 (6.92)	SS > ONAP***, AP > ONAP**
Psychiatrist	74.42 (3.86)	85.07 (4.39)	43.75 (8.91)	83.33 (6.92)	SS > ONAP***, AP > ONAP**
Community psychiatric nurse	6.98 (2.25)	7.46 (3.23)	6.67 (4.63)	6.25 (4.35)	ns
Occupational therapist	4.65 (1.86)	5.97 (2.92)	0.00	6.67 (4.63)	ns
Clinical psychologist	7.75 (2.36)	7.46 (3.23)	9.38 (5.24)	6.67 (4.63)	ns
General medical sector	2.33 (1.33)	0.00	9.38 (5.24)	0.00	ONAP > SS*
Primary care physician	1.55 (1.09)	0.00	6.25 (4.35)	0.00	ONAP > SS*
Nonpsychiatrist specialist	0.78 (0.78)	0.00	3.13 (3.13)	0.00	ns
Social worker	22.48 (3.69)	25.37 (5.36)	15.63 (6.52)	23.33 (7.85)	ns
Traditional Chinese medicine	0.78 (0.78)	1.49 (1.49)	0.00	0.00	ns
Any health service or treatment	79.84 (3.55)	86.57 (4.20)	56.25 (8.91)	90.00 (5.57)	SS > ONAP***, AP > ONAP**

Note: AP, affective psychoses; ONAP, other non-affective psychoses; NAP, non-affective psychoses; ns, not significant; SS, schizophrenia-spectrum.

^aChi-square tests were performed for group comparison.

*P < .05, **P < .01, ***P < .001.

Discussion

The HKMMS is one of the few epidemiological surveys reporting prevalence rates of specific psychotic disorders other than schizophrenia and broadly-defined categories of psychoses. The study is also among the very few general population studies which adopted a 2-phase design utilizing information from clinical reappraisal interview and medical records for diagnostic ascertainment. Our results showed that lifetime prevalence of any psychotic disorder in the Hong Kong Chinese adult population was approximately 2.5%. NAP (2.17%) was more common than affective psychoses (0.64%), and schizophrenia was the most prevalent specific psychotic disorder, with lifetime prevalence of 1.25%.

Methodological Limitations

Several methodological limitations should be considered prior to interpreting the study results. First, similar to many previous community-based epidemiological surveys, we did not include people who were homeless, incarcerated or institutionalized. As prevalence of psychosis in these excluded population segments is significantly higher than in the community,^27–29 our results would likely underestimate lifetime rates of psychotic disorders in the entire Chinese adult population of Hong Kong. Second, nonparticipation in the survey might introduce bias in prevalence estimation. Nonetheless, the attrition effect was minimized by applying weighting procedure for nonresponse adjustment. Third, the cross-sectional study design precluded us from drawing conclusions about causal relationships between identified correlates and psychotic disorders. Fourth, although household sampling strategy enabled us to detect “untreated” cases of psychotic disorders in the community (vs studies examining “treated” populations identified through case-registers¹² or sampled from more extended treatment facilities including public specialized psychiatric services, community centers providing care to mentally ills, private psychiatrists and general practitioners^30,31), in the context of studying low-prevalence disorders like psychotic disorders, this method of case ascertainment might not yield adequate number of cases for more refined epidemiological and clinical analyses.³² Fifth, given the significant variations between Hong Kong and Mainland China regarding the degrees of urbanicity, population density and economic development, and socio-cultural profiles, our data might not be generalizable to the rest of China.

Lifetime Prevalence Estimates

Our prevalence rates of NAP and schizophrenia were comparatively higher than those in many previous population-based studies. However, these epidemiological surveys themselves demonstrated marked variations in lifetime prevalence of schizophrenia in different geographic areas, ranging between 0.12% and 1.9%.^{9,12,13,33–48} A meta-analytic review revealed an almost 8-fold cross-study difference in lifetime prevalence of schizophrenia.⁶ Results of the recently published World Health Survey (WHS) also showed considerable cross-country heterogeneity in lifetime prevalence (0.07%–5.7%) of schizophrenia.⁴⁹ There is evidence suggesting that estimated prevalence varied with differences in economic status and degree of urbanicity of the regions studied. Some prior reports found that developed countries⁶ and urban areas^9,14,43,48 yielded higher prevalence than developing countries and rural areas. Methodological variation also contributes to a large discrepancy in prevalence estimates. Evidence indicates that epidemiological surveys with higher study quality^6,7 and using additional sources of information such as medical records or case-registers to supplement clinical reappraisal interviews for diagnostic assessment^12,38 reported higher prevalence. Hong Kong is a highly urbanized, densely populated city and is categorized by the World Bank as a high-income economy.⁵⁰ The specific geospatial and socioeconomic profiles of Hong Kong, alongside our wide age coverage (16–75 years) and more comprehensive diagnostic verification procedures incorporating semi-structured interview and medical record data might explain an increase in case detection and higher prevalence estimates. Of note, our findings of low prevalence rates in men aged 16–30 years, as compared to the other age groups, were unexpected and in contrast to the literature.³² These results, however, might partly be attributable to an underrepresentation of males and younger age groups in our survey sample (relative to the Hong Kong adult population) even though weighting procedure was applied to adjust for potential nonparticipation bias, and should be viewed with caution.

Very few general population studies have examined lifetime prevalence of specific psychotic disorders other than schizophrenia. Our results indicated that schizoaffective and schizophreniform disorders were rare in the community. No participant was diagnosed with brief psychotic disorder. Overall, our findings are broadly consistent with those few population-based surveys^{12,33,35,37,38,40,42,45} suggesting that these disorders were the least prevalent diagnoses among various specific psychotic disorders. Lifetime prevalence of delusional disorder also largely accords with the results of previous studies. An earlier review reported lifetime prevalence of delusional disorder ranging between 0.024% and 0.03%.⁵¹ More recent population-based surveys revealed lifetime estimates with a range from 0.048% to 0.18%.^12,35 Nonetheless, prevalence of delusional disorder is likely to be an underestimate, as individuals with the disorder rarely seek treatment due both to a lack of insight and to relatively preserved functional capacity. The non-bizarre and circumscribed nature of delusions also makes delusional disorder difficult to diagnose accurately from a single semi-structured interview, particularly when no additional sources of information are available for verification.

We found that lifetime prevalence of BP with psychotic features was 0.31%. To our knowledge, there is only one previous general population survey (Psychoses in Finland Study) examining prevalence of BP with psychotic features, reporting a lifetime estimate of 0.12%.¹² All other past population-based studies investigating prevalence of bipolar I disorder focused on an overall estimate comprising individuals with and without psychotic features. A recent review reported an aggregate cross-study lifetime prevalence of bipolar I disorder as 1.2% (range: 0.1%–3.3%).⁵² Our higher prevalence compared with the Finnish study might partly be due to our wider age coverage for survey sampling (16–75 years vs ≥30 years). Given that the onset of BP frequently occurs in young adulthood, exclusion of subjects aged below 30 years might underestimate prevalence by missing those cases with earlier age of illness onset. Our lifetime prevalence of MDD with psychotic features is close to the lower range (0.33%–0.6%) of those reported by the few prior population-based surveys.^12,53,54

Correlates and Service Utilization

The findings that schizophrenia-spectrum disorder was associated with unemployment, low personal income, and single or divorce/separated marital status are in keeping with the literature, which indicates that individuals with schizophrenia are significantly more likely to be socioeconomically disadvantaged.⁵⁵ People with a positive family history of psychosis were found to be significantly more likely to have schizophrenia-spectrum disorder or affective psychoses. Consistent with 2 systematic reviews^5,6 and previous epidemiological surveys conducted in the Chinese populations of Hong Kong,⁴⁰ Mainland China⁴⁸ and Taiwan,³⁵ we found no sex difference in prevalences of schizophrenia-spectrum disorder and other NAP. This is, however, discordant with the evidence indicating higher incidence of schizophrenia in men than women.⁵⁶ One plausible explanation for such discrepancy is that males with schizophrenia and related psychoses have shorter lifespan than female counterparts. In fact, a recent meta-analysis on schizophrenia samples has revealed significantly lower average life expectancy for men than women.⁵⁷ Accumulating evidence has further suggested than men have a higher mortality rate than women, particularly in the early course of illness.⁵⁸ Conversely, our result of lack of sex difference in lifetime prevalence of MDD with psychotic features was unexpected and contrary to some previous studies demonstrating female preponderance in this disorder.^53,54 This, however, should be interpreted with caution as accuracy in sex ratio estimation was likely compromised by small sample size (n = 15) of the disorder. Our finding that current smoking status was associated with an increased odds ratio to schizophrenia-spectrum disorder concurs with a substantial body of research demonstrating significantly higher prevalence of tobacco use in schizophrenia patients compared to the general population.⁵⁹ Although there is emerging evidence that cigarette smoking may increase the risk for psychosis,^60,61 the cross-sectional design of our study precluded us from examining the directionality of the associations between smoking and schizophrenia-spectrum disorder. Likewise, further clarification of the potential mechanisms (social drift vs social causation) underlying the associations between sociodemographic correlates and psychotic disorders could not be addressed by this study.

Our study revealed that substance use in the past year was significantly associated with other NAP, but not with schizophrenia-spectrum disorder or affective psychoses. This was at odds with most previous studies conducted in western countries which showed that schizophrenia patients had markedly higher rates of comorbid substance use than the general population.^31,62 It is noteworthy that our very low 12-month prevalence of substance use (1.8%), possibly biased by under-reporting, may obscure the potential relationship between substance use and psychotic disorders. It should also be acknowledged that comorbid substance abuse is much less frequently observed in our psychosis samples compared to those in western populations. One previous study showed that only 5.6% of Chinese first-episode psychosis patients had concurrent substance use disorder.⁶³ Victimization experiences have recently been identified as a putative risk factor for psychosis (in particular childhood adversity and trauma).⁶⁴ Here, our findings of an association with psychotic disorders accords with the second UK Adult Psychiatric Morbidity Survey, in which people with psychosis were significantly more likely to experience victimizing events than the general population and those with other nonpsychotic mental disorders.⁶⁵ Our results further suggested that victimization exposure might be more strongly related to affective psychoses than other broadly-defined psychoses. Nonetheless, our results on the associations between victimization and psychotic disorders should be interpreted with caution. First, assessment of victimization was based on retrospective self-reports which are subject to recall bias. Second, information about the timing of victimization exposure and onset of psychosis was not collected. Hence, we were not able to examine the temporal relationship between victimization and psychosis development. Furthermore, patients with established psychotic disorders are also found to be susceptible to victimization.^66,67 Prospective investigation with refined measurement of victimization experience is warranted to clarify its impact on risk for psychosis.

Our findings that 3-quarters of participants with psychotic disorder reported specialist mental health treatment in the 12 months preceding interview is consistent with the literature which finds that the vast majority of people with psychosis are in contact with the health service system.⁶⁸ A significantly greater proportion of participants (above 80%) with schizophrenia-spectrum disorder or affective psychoses visited mental health professionals than those with other NAP (less than 50%). This may probably reflect aspects of the illness in specific psychotic disorders of other NAP (eg, poor insight in delusional disorder and potentially milder illness severity of psychotic disorder NOS that evades early detection), resulting in lower rates of help-seeking behavior.

Conclusion

Our results indicate that approximately 2.5% of the Hong Kong Chinese adult population had a lifetime diagnosis of psychotic disorder, constituting a considerable burden to patients, families and society. This underscores an urgent need to improve the effectiveness of individual treatments and healthcare delivery systems in order to enhance early recovery from these severe mental disorders.

Supplementary Material

Supplementary data are available at Schizophrenia Bulletin online.

Funding

This study was supported by the Health and Health Services Research Fund (Ref: 09101601) of the Food and Health Bureau, the Government of Hong Kong Special Administrative Region.