People living with psychotic illness 2010

2. Estimates of the prevalence of psychotic disorders

Page last updated: November 2011

The prevalence of a disorder is the proportion of people who meet diagnostic criteria for that disorder in a defined population over a particular period. Rates of incidence, remission, relapse and premature mortality influence prevalence estimates. However, from a policy perspective, prevalence is a key index as it indicates the number of people in the population who are in need of facilities, treatment and support.

Specification of a particular population and period are critical to the measurement and interpretation of any estimate of prevalence. The population is a defined group of people at risk for the disorder of interest. In the case of the second national psychosis survey, it is defined by geographic and age criteria, referring to people between the ages of 18 and 64 years who were resident in Australia during the survey period.

It is also confined to those people who received services from publicly funded services, both specialised mental health services and non-government organisations. The survey did not cover private service providers, that is private psychiatrists, psychologists and private hospitals and, as such, the prevalence does not cover those individuals who only received services through these providers.

The method used to calculate prevalence estimates is described fully in appendix 2. Briefly, the proportion of people attending public specialised mental health treatment services in the survey census month who met criteria for a diagnosis of interest was estimated using appropriately weighted screen positive and screen negative subsamples in whom diagnostic status was ascertained using the diagnostic module of the Diagnostic Interview for Psychosis.4 This determines whether an individual meets the criteria of the standard diagnostic classification system used by clinicians, which is the International Classification of Diseases 10th Revision (ICD-10).

From this proportion, the number of people meeting diagnostic criteria in the census month was calculated for each site. Prevalence at each site was this number as a fraction of the estimated population of the catchment in each age and sex stratum. Aggregate estimates were obtained by combining prevalence estimates at each site weighted by the proportion of the total population represented by each site. For estimates combining strata, adjustments were made to reflect the age and sex distributions of the Australian population aged 18-64 years.

Two forms of contact with services were estimated, contact with public specialised mental health services and contact with non-government organisations funded to support people with psychotic illnesses.

2.1 One-month treated prevalence of persons with psychotic disorders in contact with public specialised mental health services
2.2 12-month treated prevalence of persons with psychotic disorders in contact with public specialised mental health services

2.1 One-month treated prevalence of persons with psychotic disorders in contact with public specialised mental health services

Table 2.1 shows the estimated one-month prevalence of people with an ICD-10 psychotic illness in contact with public specialised mental health services in Australia by age and sex.

Weighted to reflect the sex and age distribution of the Australian population aged 18 to 64 years, the overall prevalence of people meeting criteria for diagnosis of an ICD-10 psychotic disorder is 3.1 cases per 1,000 population. The corresponding prevalences for males and females, each weighted to reflect population age distributions, are 3.7 and 2.4 cases per 1,000 population respectively.

Prevalence is higher for males than females in every age group except the oldest group of those aged 55-64 years, in which it was 1.8 and 2.2 cases per 1,000 population respectively.

As can be seen in figure 2-1, prevalence in males rises sharply from 2.5 cases per 1,000 population in 18-24 year olds to 5.2 cases per 1,000 population in 25-34 year olds and 4.7 cases per 1,000 population in 35-44 year olds.

Prevalence in females climbs less markedly, rising from 1.6 cases per 1,000 population in 18-24 year olds to 2.6 cases per 1,000 population in 25-34 year olds. It is then relatively stable across the lifespan covered by the survey.

Based on the survey catchments it was estimated that nationally, almost 44,000 people with psychotic disorders receive services from public specialised mental health services in a one-month period. Three-fifths (60.7%) of these people are male and a similar proportion (60.8% or 26,625 persons) are in the older age group (35-64 years of age). Top of page

Table 2-1. Estimated national one-month treated prevalence of ICD-10 psychotic disorders in public specialised mental health services and number of people in contact with services

Table 2-1 is separated into 3 smaller tables in this HTML version for accessibility reasons. It is presented as one table in the PDF version.

Males

Age (years)Catchment ERP*Australian ERPPrevalence (cases per 1000)Estimated persons**
18 – 24 #
117,596
1,167,678
2.5
2,929
25 – 34
161,314
1,613,064
5.2
8,406
35 – 44
156,498
1,574,669
4.7
7,453
45 – 54
147,866
1,508,028
3.7
5,525
55 – 64
120,137
1,260,193
1.8
2,287
18 - 64
703,411
7,123,632
3.7
26,600

Females

Age (years)Catchment ERP *Australian ERPPrevalence (cases per 1000)Estimated persons **
18 – 24 #
111,731
1,100,550
1.6
1,714
25 – 34
158,354
1,586,242
2.6
4,140
35 – 44
158,092
1,594,048
2.8
4,438
45 – 54
149,953
1,537,401
2.7
4,099
55 – 64
124,102
1,278,357
2.2
2,823
18 - 64
702,232
7,096,598
2.4
17,215

Persons

Age (years)Catchment ERP *Australian ERPPrevalence (cases per 1000)Estimated persons **
18 – 24 #
229,327
2,268,228
2.0
4,644
25 – 34
319,668
3,199,306
3.9
12,546
35 – 44
314,590
3,168,717
3.8
11,891
45 – 54
297,819
3,045,429
3.2
9,624
55 – 64
244,239
2,538,550
2.0
5,110
All persons
1,405,643
14,220,230
3.1
43,815

* ERP - Estimated resident population for 2010 extrapolated from 2009 data provided by the Australian Bureau of Statistics
** Estimated totals for ages 18-64 may not equal the sum of the individual age groups due to rounding
# The 18-24 year age group covers seven years only in contrast to the 10 years in each of the older groups

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Figure 2-1. Estimated national one-month treated prevalence of ICD-10 psychotic disorders in public specialised mental health services by sex

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Refer to the following table for a text equivalent of figure 2-1 - estimated national one-month treated prevalence of ICD-10 psychotic disorders in public specialised mental health services by sex

Text version of figure 2-1

AgeMales - prevalence (cases per 1,000)Females - prevalence (cases per 1,000)Persons - prevalence (cases per 1,000)
18 - 242.511.562
25 - 345.212.623.9
35 - 444.732.773.8
45 - 543.662.643.2
55 - 641.812.272
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Figure 2-2. Estimated number of people with ICD-10 psychotic disorders in contact with public specialised mental health services in one month by sex


Refer to the following table for a text equivalent of figure 2-2: estimated number of people with ICD-10 psychotic disorders in contact with public specialised mental health services in one month by sex

Text version of figure 2-2

AgeMalesFemalesPersons
18 - 242,9291,7144,644
25 - 348,4064,16312,546
35 - 447,4534,41911,891
45 - 545,5254,0619,624
55 - 642,2872,8985,110
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2.2 12-month treated prevalence of persons with psychotic disorders in contact with public specialised mental health services

Table 2-2 shows the estimated 12-month prevalence of people with an ICD-10 psychotic disorder in contact with public specialised mental health services in Australia by age and sex. The overall prevalence is 4.5 cases per 1,000 population. The corresponding prevalences for males and females are 5.4 and 3.5 cases per 1,000 population, respectively.

As with the one-month prevalence estimates, 12-month prevalence is higher for males than females in every age group except the oldest group (55-64 years), with prevalence in males rising sharply from 4.0 cases per 1,000 population in 18-24 year olds to 7.4 cases per 1,000 population in 25-34 year olds and 7.1 cases per 1,000 population in 35-44 year olds.

Prevalence in females rises from 2.3 cases per 1,000 population in 18-24 year olds to 3.8 cases per 1,000 population in 25-34 year olds. It is then relatively stable across the lifespan covered by the survey.

Nationally, it was estimated 63,533 people with psychotic disorders received services from public specialised mental health services in a 12-month period. Three-fifths (61.2%) of these people were male and a similar proportion (60.4% or 38,363 persons) were in the older age group (35-64 years of age). Top of page

Table 2-2. Estimated national 12 month treated prevalence of ICD-10 psychotic disorders in public specialised mental health services and number of people in contact with services

Table 2-2 is separated into 3 smaller tables in this HTML version for accessibility reasons. It is presented as one table in the PDF version.

Males

Age (years)Catchment ERP *Australian ERPPrevalence (cases per 1000)Estimated persons **
18 – 24 #
117,596
1,167,678
4.0
4,644
25 – 34
161,314
1,613,064
7.4
11,975
35 – 44
156,498
1,574,669
7.1
11,175
45 – 54
147,866
1,508,028
5.2
7,794
55 – 64
120,137
1,260,193
2.6
3,273
18 - 64
703,411
7,123,632
5.4
38,859

Females

Age (years)Catchment ERP *Australian ERPPrevalence (cases per 1000)Estimated persons **
18 – 24 #
111,731
1,100,550
2.3
2,499
25 – 34
158,354
1,586,242
3.8
6,051
35 – 44
158,092
1,594,048
3.9
6,268
45 – 54
149,953
1,537,401
3.8
5,785
55 – 64
124,102
1,278,357
3.2
4,069
18 – 64
702,232
7,096,598
3.5
24,674

Persons

Age (years)Catchment ERP *Australian ERPPrevalence (cases per 1000)Estimated persons **
18 – 24 #
229,327
2,268,228
3.1
7,144
25 – 34
319,668
3,199,306
5.6
18,026
35 – 44
314,590
3,168,717
5.6
17,443
45 – 54
297,819
3,045,429
4.5
13,579
55 – 64
244,239
2,538,550
2.9
7,341
All persons
1,405,643
14,220,230
4.5
63,533

* ERP - Estimated resident population for 2010 extrapolated from 2009 data provided by the Australian Bureau of Statistics
** Estimated totals for ages 18-64 may not equal the sum of the individual age groups due to rounding
# The 18-24 year age group covers seven years only in contrast to the 10 years in each of the older groups