People living with psychotic illness 2010

Appendix 1. Background, aims and methodology

Page last updated: November 2011

Catchment sites
Census month
Inclusion criteria
Exclusion criteria
Coverage
Generalisability
Interview sample
Prevalence
Psychosis screener
Interview schedule
Comparison data

Catchment sites

  • New South Wales
    • Hunter New England
    • Orange
  • Queensland
    • West Moreton
  • South Australia
    • Northern Mental Health
  • Victoria
    • North West Area Mental Health Service
    • St Vincent's Mental Health Service
  • Western Australia
    • Fremantle, Peel and Rockingham and Kwinana
Catchment site profiles are provided in appendix table 1-3.

Census month

March 2010

Inclusion criteria

Diagnosis

Census month: screen-positive rating for psychosis on the Psychosis Screener

11 months prior to census: a diagnosis of psychosis on administrative records, namely, ICD-10 schizophrenia (F20), schizotypal disorder (F21), persistent delusional disorder (F22), acute or transient psychotic disorder (F23), induced delusional disorder (F24), schizoaffective disorders (F25), other and unspecified non-organic psychotic disorder (F28, F29), manic episode with psychotic symptoms (F30.2), bipolar affective disorder with psychotic symptoms (F31.2, F31.5), severe depressive episode with psychotic symptoms (F32.3), recurrent depressive disorder with psychotic symptoms (F33.3) OR at least two admissions with a drug- or alcohol- induced psychosis (F10-F19: .5 and .7 only)

People may experience transient psychotic symptoms related to acute substance intoxication or withdrawal. These disorders are the not the focus of the current survey. However, the links between psychotic disorders and substance misuse are complicated and many individuals with psychotic disorders have co-morbid alcohol or illicit drug use/dependence disorders. A case of psychosis may be missed if the primary diagnosis at the time of an inpatient admission is a substance-induced psychosis, masking an underlying psychotic disorder. For this reason, screening of administrative registers in the 11 months prior to the census month included screening for people with at least two inpatient admissions with a substance-induced psychosis. Only 1.8% of the total number screen positive for psychosis met this criterion. If they did not meet full criteria for a psychotic disorder at the time of interview, they were coded as "other" in the diagnostic groupings.

Age range

Aged 18-64 years during the census month.

Residency

Resident in designated postcodes/suburbs as determined by the catchment area of the relevant mental health services.Top of page

Exclusion criteria

The survey excluded:
  • people with insufficient English or a communication or cognitive impairment that would interfere with a person's capacity to give informed consent and to complete a valid interview; and
  • those unavailable for screening or interview due to residence in a nursing home or prison.

Coverage

The survey targeted:
  • people in contact with public specialised mental health services in March 2010, that is including inpatient units, emergency departments, community liaison, public outpatient and community care mental health services units, but excluding drug and alcohol services;
  • people who used public specialised mental health services in 11 months prior to March 2010, that is from April 2009; and
  • people in contact with non-government organisations funded to support people with mental illnesses in March 2010 census month.
Screening identified 7,955 people who were screen positive for psychosis (appendix table 1-1). These were adults aged 18-64 years in contact with public specialised mental health services between April 2009 and March 2010 inclusive, as well those receiving mental health services from government funded non-government organisations in March 2010.

Just over half (56.4%) were current clients of the public specialised mental health services, that is in March 2010.

To enumerate people only using non-government organisations funded to support people with mental illnesses in the census month, all potential non-government agencies were invited to participate in the census.
  • Overall, 86% of individual centres that were part of these non-government organisations and located within the survey catchment area participated.
  • In general, those not participating were smaller centres within larger participating organisations, predominantly in rural areas.
  • These data were used in national prevalence estimates.
The survey did not enumerate certain groups of people:
  • those under the age of 18 years or those over the age of 64 years;
  • those who did not make contact with public specialised mental health services within the selected 12-month period or non-government organisations funded to support people with mental illnesses in the census month; and
  • those who, in the census month, were solely in contact with general practitioners or private psychiatrists and psychologists, or who were homeless and not in contact with treatment services.
Homeless people were not a specific target for enumeration since this group was covered in the 1997-98 psychosis survey where they represented a small proportion of the census month sample. The 1997-98 survey also found that the majority of people who had been homeless in the census month had had some contact with treatment services in the previous 11 months or between screening and interview. Consequently, the current survey elicited comprehensive data on primary, secondary and tertiary homelessness at any point in the 12-month period prior to interview from all survey participants.
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Appendix Table 1-1. People who were screen positive for psychosis by sector

Persons Proportion (%)
Used public specialised mental health services in the census month
4,489
56.4
Used public specialised mental health services in the 11 months prior to census month
2,540
31.9
Only used non-government organisation funded to support people with mental illnesses in the census month
926
11.6
Total
7,955
100.0

Appendix Figure 1-1. Service use by people with psychotic illness and who was included in 2010 national psychosis survey

Refer to the following text for a text equivalent of appendix figure 1-1. Service use by people with psychotic illness and who was included in 2010 national psychosis survey
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Text version of Appendix Figure 1-1

Of all people with a psychotic illness in the period of April 2009 - March 2010, people aged 0-17 and 65+ years were not included in the survey sample. People aged 18-64 years who did not receive mental health services between April 2009 - March 2010 were not included in the survey sample. People aged 18-64 who received mental health services between April 2009 - March 2010 were divided into three categories:
      • People who received public mental health service +/- other NGO and private sector. People who received these services in March 2010 (4,489) and April 2009 - February 2010 (2,540) were all included in the survey sample.

      • People who received NGO services only +/- private sector. People who received these services in March 2010 (926) were included in the survey sample. People who received these services between April 2009 - February 2010 were not included in the survey sample.

      • People who received private sector mental health services only (including private psychiatrists, general practitioners, private hospitals, and psychologists, other allied health). These people were not included in the survey sample.
7,955 people were identified through the three cohort entry pathways. Of these, a sample of 1,825 was randomly selected for interview.

Generalisability

These data were collected using a two-phase design, recognised in the research literature as appropriate for the collection of data on low prevalence disorders.27, 28 Through its national, epidemiological approach to sampling, the survey catchment sites represented 10% of Australians aged 18-64 years, ensuring generalisability of the survey data to all people with psychosis in contact with public sector treatment services over a one-year period in Australia.

Interview sample

In total, 1,825 people completed interviews. These people were randomly selected by age group and catchment site from the 7,955 people who were screen-positive for psychosis and who met survey eligibility criteria.

To be eligible for interview, participants required positive ratings for at least two items on the screening instrument. These items covered hallucinations and delusions (six items), and being on antipsychotic medication (key worker form) or told by a doctor that they had a psychotic disorder (participant form). Alternatively, they were eligible if they had a recorded diagnosis of psychosis or two admissions with a drug or alcohol induced psychosis in the 11 months prior to census.

Not all eligible people, however, met full diagnostic criteria for psychosis when interviewed by trained mental health professional staff using the detailed Diagnostic Module of the Diagnostic Interview for Psychosis4 to elicit the signs and symptoms of psychotic disorders. Nonetheless, people interviewed represent the range of severe disorders, with associated disability and comorbidities, presenting to public specialised mental health services at any point in time.

Participation by those screen-positive and selected for interview was 29% overall.

There were a number of reasons for non-participation.
  • Passive non-response that is people being selected from the census under random sampling, but ultimately not directly asked to participate, was a significant cause of non-participation. Passive non-responders made up 47% of all non-responders. There were several reasons why they were not contacted:
    • One quarter (27%) were eligible but contact was not made, either because they could not be tracked or because they had died in the period since screening.
    • For 10% of cases, case managers had not invited clients to participate because they had assessed them as not being well enough or, in some cases, had neglected to pass on the request.
  • Ten percent (10%) were judged by the interviewers to be too unwell physically or mentally to provide consent.
  • Almost half (47%) had refused.
  • A small proportion (6%) had agreed, but could not find a time to be interviewed.
With the exclusion of those not given the opportunity to participate (passive non-responders), the response rate is 44% overall. This is generally consistent with the results of the 1997-98 survey and comparable to similar studies internationally. Higher response rates are not typically found in surveys of people who have psychotic illness or for surveys of more unwell populations.
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Appendix Table 1-2. Full interview sample by sector

Males
(%)
Females
(%)
Aged 18-34 years
(%)
Aged 35-64 years
(%)
Persons
(%)
Used public specialised mental health services in the census month
66.9
65.6
66.8
66.1
66.4
Used public specialised mental health services in the 11 months prior to census month
21.7
23.4
25.1
20.4
22.4
Only used non-government organisation funded to support people with mental illnesses in the census month
11.4
11.0
8.2
13.5
11.2
Total
1,087
738
773
1,052
1,825

Interviewing those without psychosis

In addition to the screen positive sample, 164 people were randomly selected for interview from the pool of people who were screened as negative for psychosis. This group completed the diagnostic module only and their data were used in the determination of census group and population prevalence.

Sample bias

To assess whether non-participation had introduced a systematic bias into the data collection, the demographic and psychosis screening data for those interviewed were compared with data for those
selected for interview, but who did not participate for any reason.
  • Both groups were similar in terms of sex, with 60% of those interviewed male compared with 62% of those selected but not interviewed.
  • The proportions in each age group were similar, with 44% of those interviewed aged 18-34 years at the time of screening compared with 43% of those not interviewed.
  • The psychosis screening profiles for both groups were very similar indicating no marked differences in terms of lifetime symptom profiles based on the screener items. There were no differences on six of the eight screener items. There were differences of three and four percentage points for delusional mood and delusions of persecution respectively, with the proportion lower in the interviewed sample, but no differences on the other three delusional items or all delusional items combined.

Prevalence

The prevalence of psychosis is based upon estimates of the number of people who met the ICD-10 diagnostic criteria for psychosis. These disorders include schizophrenia, schizoaffective disorder, depressive psychosis and other psychotic disorders.

It is largely limited to those being treated through public specialised mental health services.

It does not take account of the large numbers of people receiving services through the public system who do not have a psychotic illness nor does it take account of those with psychosis being treated only in the private sector.

Data from the Orange catchment were not included in the prevalence estimates. Geographic and operational factors at this site made fulfilment of the sampling framework unfeasible. This would have resulted in large or undefined weights for many strata, yielding prevalence estimates of uncertain validity. Orange data were included in all the descriptive statistics where the issues that precluded their use in prevalence estimates had little impact.

Psychosis screener

The psychosis screener used for census month screening was developed as part of the first national psychosis survey and its psychometric properties have been published.2-3 For the second survey, pre-enumeration piloting led to enhancements that further improved its psychometric properties.

The screener consists of seven questions targeting specific psychotic symptoms (over the lifetime) and an eighth item recording the clinical judgement of the mental health professional administering the screener whether, on the basis of all the information available, psychotic symptoms had ever been present and the person met the criteria for inclusion.
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Interview schedule

The interview schedule comprised of 32 modules in total. These included a number of embedded instruments, as well as some modules that have been specifically designed for this survey.

The Diagnostic Interview for Psychosis – Diagnostic Module (DIP-DM)4 was developed for use by trained mental health professionals in the first Australian survey of psychosis in 1997-98.2-3 It uses SCAN prompts29 to draw out signs and symptoms, then applies the OPCRIT criteria developed by Farmer et al30 using a computer algorithm to generate diagnoses according to, among others, ICD-10 and DSM-IV classification systems. It has well established psychometric properties4 and has been translated into eight languages for use internationally in psychosis surveys and studies and in clinical settings.

Other modules covered the following:
  • Demographics, social participation and functioning: 1 General Information; 2 Education; 3 Housing; 4 Activities of daily living; 5 Employment 6 Child care; 7 Caring; 8 Global work ratings; 9 Childhood experiences; 10 Socialising; 11 Finances; 12 Crime and offending; 13 Personal safety; 14 Satisfaction with life; 15 Global functioning ratings

  • Physical Health: 16 Nutrition; 17 Physical activity; 18 Physical health and metabolic measures Quality of life: 19 Assessment of Quality of Life

  • Psychopathology and cognition: 20 Diagnostic Interview for Psychosis (Diagnostic Module); 21 Negative symptoms; 22 Worry, panic, anxiety and obsession; 23 Cognition

  • Service use and perceived need: 24 Inpatient; 25 Emergency; 26 Outpatient; 27 Public community mental health; 28 Community rehabilitation and day therapy; 29 General practice; 30 Medication use; 31 Non-government agencies; 32 Mental health care and unmet need
A number of externally developed instruments were used in their entirety, namely:
  • Assessment of Quality of Life31
  • Alcohol Use Disorders Identification Test32
  • CAGE33
  • Carpenter: World Health Organization Schedules for Clinical Assessment in Neuropsychiatry items of the Carpenter Deficits syndrome29,34
  • Fagerstrom Test for Nicotine Dependence35
  • International Physical Activity Questionnaire (short format)18
  • Multidimensional Scale of Independent Functioning9
  • National Adult Reading Test14
  • Personal and Social Performance Scale10
  • RBANS Digit Symbol Coding Test20

Comparison data

The three main sources of comparison data in this report are:
  1. The first Australian psychosis survey, the Survey of Low Prevalence (Psychotic) Disorders;2, 3
  2. Population data from the 2007 National Survey of Mental Health and Wellbeing, a household survey of people aged 16-85 years designed to estimate the prevalence of common mental disorders in the Australian general population6, 8, 19; and
  3. Australian Bureau of Statistics data, referenced as appropriate. Many of the survey questions were derived from these sources to ensure comparability.
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Appendix Table 1-3. Catchment site population profiles

NSW
Hunter New England
NSW
Orancge
QLD
West Moreton
SA
Northern
VIC
North West
VIC
St Vincent's
WA
Fremantle, Peel and Rockingham Kwinana
Australia
Estimated Resident Population (2010, extrapolated) aged 18-64 (n) (a)
378, 935
83,711
135,407
230,400
207,962
172,485
280,454
Females (2010, extrapolated) aged 18-64 (%) (a)
49.7
49.4
49.8
50.4
50.2
50.5
49.6
Estimated Resident Population (June 2009) aged 18-64 (n) (b)
372,705
82,352
133,230
226,654
204,548
169,512
275,922
14,220,230
Females (June 2009) aged 18-64 (%) (b)
49.7
49.4
49.8
50.3
50.2
50.4
49.5
49.9
Area (square kilometres (c)
22,554.7
27,701.5
6,660.1
814.7
554.6
79.5
3,317.1
-
Population density (total population per km2) (b)
26.4
4.9
31.0
432.4
557.1
3,049.3
128.1
2.9
Population age structure (c)
Population aged 0-17 (%)
24.2
26.5
28.4
25.0
24.6
19.4
24.4
24.0
Population aged 18-64 (%)
60.6
58.5
61.0
62.8
63.2
67.6
61.4
62.7
Population aged 65 years and over (%)
15.2
14.9
10.5
12.2
12.2
13.0
14.2
13.3
Other characteristics (c)
Indigenous persons (all ages) (%)
2.6
4.5
3.1
1.6
0.5
0.2
1.4
2.3
Australian-born (all-ages) (%)
85.0
88.2
78.9
70.7
62.1
66.6
65.0
70.9
Language spoken at home-English only (all ages) (%)
91.9
93.3
88.9
83.7
56.6
72.5
83.7
78.5
Marital Status (15 years and over) (c) - Never married
31.2
31.4
32.4
32.3
35.6
42.6
31.0
33.2
Family Structure (c)
One parent family (%)
17.3
16.1
18.1
18.8
17.2
12.9
14.9
15.8
Couple family without children (%)
38.1
39.3
35.1
35.7
30.7
37.6
39.3
37.2
Couple family with children (%)
43.2
43.2
45.4
44.2
49.9
46.3
44.4
45.3
Other family (%)
1.4
1.4
1.4
1.3
2.2
3.2
1.4
1.7
Total (%)
100
100
100
100
100
100
100
100
Employment Status (15 years and over) (c)
Employed (%)
53.2
55.6
57.8
56.5
53.8
61.4
56.5
57.2
Unemployed (%)
3.9
3.6
3.1
3.4
3.8
2.8
2.4
3.2
Not in labour force/Not stated (%)
42.9
40.9
39.2
40.1
42.5
35.9
41.2
39.6
Total (%)
100
100
100
100
100
100
100
100
Median Weekly Income (15 years and over) (c)
339.0
403.4
447.9
428.2
407.7
644.6
471.0
466.3
Same usual residence (c)
One year ago (%)
80.0
78.7
75.1
81.3
79.8
75.7
74.1
77.3
Five years ago (%)
53.4
50.5
44.9
55.2
54.3
48.9
44.6
49.6
Private, occupied dwellings by tenure type (c)
Fully owned (%)
35.5
37.0
29.0
28.9
32.8
32.3
31.9
32.6
Being purchased (%)
31.9
30.4
37.4
40.9
35.3
26.1
36.2
32.2
Being rented (%)
25.1
25.1
26.1
23.3
23.2
32.5
22.7
26.1
Other/Not stated (%)
7.5
7.6
7.5
6.9
8.7
9.1
9.2
9.1
Total (%)
100
100
100
100
100
100
100
100
Persons by dwelling type (c)
Separate house (%)
88.8
92.5
95.5
89.5
82.0
56.7
88.6
81.2
Semi-ducted, terrace, townhouse (%)
5.5
2.6
1.8
7.3
9.6
22.3
7.0
7.5
Flat, unit, apartment
4.7
3.7
1.7
2.7
7.9
20.2
3.8
9.9
Other/Not stated (%)
1.1
1.1
1.0
0.4
0.5
0.8
0.7
1.3
Total (%)
100
100
100
100
100
100
100
100
Educational Attainment (18 to 64 years) (c)
School level qualification only or had not attended school
47.3
49.1
54.7
56.2
49.2
29.3
45.3
45.6
Proportion of Collection Districts by Remoteness Area (d)
Major cities (%)
68.9
0.0
70.6
97.9
98.9
100.0
75.6
-
Inner regional (%)
28.1
68.6
29.2
2.1
1.1
0.0
24.4
-
Outer regional (%)
2.9
31.4
0.3
0.0
0.0
0.0
0.0
-
Total (%)
100
100
100
100
100
100
100
-
Index of Relative Socio-Economic Disadvantage (e)
986.2
978.5
970.5
962.7
975.6
1,078.2
1,023.4
-
(weighted index score and range for each catchment)
483-1159
657-1161
676-1152
567-1150
655-1134
433-1167
698-1199
-
Index of Relative Socio-Economic Advantage and Disadvantage (e)
975.5
956.5
950.5
941.1
976.3
1,121.9
1,018.0
-
(weighted index score and range for each catchment)
610-1,188
725-1,147
731-1,192
653-1,134
748-1,140
634-1,228
736-1,306
-
Index of Economic Resources (e)
984.0
979.8
988.5
968.1
985.8
1,053.5
1,038.0
-
(weighted index score and range for each catchment)
492-1,178
709-1,181
720-1,222
611-1,184
663-1,212
509-1,202
768-1,240
-
Index of Education and Occupation (e)
952.9
957.8
927.6
924.8
971.1
1161.2
994.5
-
(weighted index score and range for each catchment)
690-1,199
750-1,162
781-1,136
736-1,116
790-1,242
748-1,263
783-1,365
-

(a) Estimated Resident Population data for 2010 extrapolated from Estimated Resident Population data for 2009 (preliminary) extracted by the Australian Bureau of Statistics.
(b) Estimated Resident Population data (preliminary) for 30 June 2009 were extracted by the Australian Bureau of Statistics.
(c) Census data (2006) for the catchment areas were extracted by the Australian Bureau of Statistics using catchment area postcodes.
(d) Remoteness Area data were extracted by the ABS and are based on the Australian Standard Geographical Classification.
(e) The Socio-Economic Indexes for Areas (SEIFA) were extracted by the Australian Bureau of Statistics using catchment area postcodes to obtain postal area level indexes. The higher the score, the more positive the catchment profile. For example, the higher the Index of Relative Socio-Economic Disadvantage, the less disadvantaged the catchment area.