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  • Prevalence

    On this website the terms 'mental illness' and 'mental disorder' are both used to describe a wide spectrum of mental health and behavioural disorders, which can vary in both severity and duration. The most prevalent mental illnesses are depression, anxiety and substance use disorders.

    A program of population surveys, referred to as the National Survey of Mental Health and Wellbeing, began in Australia in the late 1990s and these surveys provide evidence on; the prevalence of mental illness in the Australian population, the amount of associated disability, comorbidity of mental disorders, and the use of health services by people with mental disorders. These studies have three main components-a population-based survey of adults, a service-based survey of people with low-prevalence psychotic disorders, and a population survey of children.

    Survey of Adult Population (aged 16-85)

    The 2007 National Survey of Mental Health and Wellbeing (NSMHWB) of adults provides information on the 12-month and lifetime prevalence of mental disorders in the Australian population. It was estimated from the survey that 45% of Australians in this age range (7.3 million people) will experience a mental disorder at some time in their life (ABS 2008). It was also estimated that 20% of the population (3.2 million people) had experienced a common mental disorder in the previous 12 months (ABS 2008). Of these, anxiety disorders (such as social phobia) were the most prevalent, afflicting 14% of the population, followed by affective disorders (such as depression) (6%) and substance use disorders (such as alcohol dependence) (5%). Readers are directed to the full report for further information (ABS 2008).

    Survey of Children and Adolescents (aged 4-17)

    A second national household survey of the mental health and wellbeing of Australian children and adolescents (Young Minds Matter) was conducted in 2013–14 with the results released in August 2015. A total of 76,606 households were approached to participate in the survey. In total, 6,310 parents and carers or 55% of the eligible households (with children in the age range 4–17) responded and 2,967 or 89% of eligible young people aged 11–17 also participated with their parent's permission.

    The survey used a diagnostic schedule to determine the prevalence of mental disorders in children and adolescents in Australia. Almost 1 in 7 (14%) of 4–17 years were assessed as having mental health disorders in the previous 12 months which is equivalent to 560,000 child and adolescents. Attention Deficit Hyperactivity Disorder (ADHD) was the most common mental disorder (a little over 7% or 298,000), followed by anxiety disorders (a little under 7% or 278,000), major depressive disorder (3% or 112,000) and conduct disorder (2% or 83,600) - see Figure 1. Almost one third (30% or 4% of all 4–17 year olds) with a disorder had two or more mental disorders at some time in the previous 12 months.


    Figure 1: Prevalence of mental disorders in the past 12 months in 4–17 year olds

    Horizontal bar chart showing the prevalence of mental disorder in the past 12 months in 4-17 year olds. ADHD was the most prevalent (just over 7%), followed by Anxiety disorder (just under 7%), Major depressive disorder (3%) and conduct disorder (2%)

    Source: Lawrence et al. 2015.


    Child and adolescent males (16%) were more likely than females (12%) to have experienced mental disorders in the previous 12 months. The prevalence of mental disorders was slightly higher for older females (13% for 12–17 year olds) than for younger females (11% for 4–11 year olds). However, the prevalence for males did not differ markedly with age.

    There were a number of significant methodological differences between the Young Minds Matter survey and the first child and adolescent survey conducted in 1998. However, it is possible to compare the prevalence data for three mental health disorders (major depressive disorder, ADHD and conduct disorder). Prevalence of depressive disorder increased from 2% to 3%, ADHD decreased from 10% to 8%, and conduct disorder decreased from 3% to 2%. Readers are directed to the full report for further information (Lawrence et al. 2015).

    Survey of People Living with Psychotic Illness (aged 16-84)

    Mental illness also includes 'low prevalence' conditions. This group includes psychotic illnesses and a range of other conditions such as eating disorders, and severe personality disorder (DoHA 2010). Psychotic illnesses are characterised by fundamental distortions of thinking, perception and emotional response. Psychotic disorders include schizophrenia, schizoaffective disorder, bipolar disorder and delusional disorder (Morgan et al. 2011).

    Estimates from the 2010 NSMHWB Survey of People Living with Psychotic Illness were that 64,000 people in Australia aged 18-64 have a psychotic illness and are in contact with public specialised mental health services each year. This equates to 5 cases per 1,000 population or 0.5% of population (Morgan et al. 2011). The survey found the most frequently recorded of these disorders was schizophrenia which accounted for almost half of all diagnoses (47%). Readers are directed to the full report for further information.

    Impact and burden

    Mental disorders can vary in severity and be episodic or persistent in nature. A recent review estimated that 2–3% of Australians (about 600,000 people) have a severe mental disorder, as judged by diagnosis, intensity and duration of symptoms, and degree of disability caused (DoHA 2013). This group is not confined to those with psychotic disorders, who represent about one-third of those with severe mental disorders; it also includes people with severe and disabling forms of depression and anxiety. Another 4–6% of the population (about 1 million people) have a moderate disorder and a further 9–12% (about 2 million people) have a mild disorder (DoHA 2013).

    In 2011, mental disorders were responsible for 754 deaths, excluding suicide and dementia, with most deaths due to substance abuse, particularly alcohol (AIHW analysis of AIHW National Mortality Database).

    Mental and behavioural disorders, such as depression, anxiety, and drug use are important drivers of disability and morbidity. The 2010 Global Burden of Disease study examined the health loss due to disease and injury that is not improved by current treatment, rehabilitative and preventative efforts of the health system and society (IHME 2013). For Australia, mental and behavioural disorders were estimated to be responsible for 12.9% of the total burden of disease in Australia in 2010, placing it third as a broad disease group after cancer and cardiovascular disease (IHME 2013).

    In terms of the non-fatal burden of disease, which is a measure of the number of years of 'healthy' life lost due to living with a disability, mental and behavioural disorders were the second largest contributor (22.3% of the non-fatal burden of disease) (IHME 2013).

    The 2003 Burden of Disease and Injury in Australia study found that depression and anxiety disorders were associated with an increased risk of ischaemic heart disease and suicide (Begg et al. 2007). The AIHW is currently updating estimates of the burden of disease for Australia, drawing on the latest information and an improved methodology, and expect to publish the results later in 2015.

    In addition, in 2013, 31.2% of people in receipt of the Disability Support Pension had a primary medical condition of 'psychological/psychiatric' (DSS 2014).

    There is an association between diagnosis of mental health disorders and a physical disorder, often referred to as a 'comorbid' disorder. From the 2007 NSMHWB of adults, 11.7% of people with a 12-month mental disorder also reported a physical condition; with 5.3% reporting two or more physical conditions.

    According to the 2010 Survey of People Living with Psychotic Illness, people with psychotic illness also frequently experience poor physical health outcomes and comorbidities (Morgan et al. 2011). For example, over one-quarter (26.8%) of survey participants had heart or circulatory conditions and one-fifth (20.5%) had diabetes (compared with 16.3% and 6.2% respectively in the general population). The prevalence of diabetes found in the National Survey of People Living with Psychotic Illness is more than three times the rate seen in the general population. Other comorbidities included epilepsy (7.3% compared with 0.8% in the general population) and severe headaches/migraines (25.4% compared with 8.9% in the general population).


    References

    Australian Bureau of Statistics (ABS) 2008. National survey of mental health and wellbeing: summary of results, Australia, 2007. ABS cat. no. 4326.0. Canberra: ABS

    Begg S, Vos T, Barker B, Stevenson C, Stanley L & Lopez A 2007. The burden of disease and injury in Australia, 2003. AIHW cat. no. PHE 82. Canberra: AIHW.

    Department of Social Services (DSS) 2014. Characteristics of Disability Support Pension Recipients, June 2013. Canberra: DSS.

    Department of Health and Ageing (DoHA) 2010. National mental health report 2010: summary of 15 years of reform in Australia’s mental health services under the National Mental Health Strategy 1993–2008. Canberra: Commonwealth of Australia.

    DoHA 2013. National Mental Health Report 2013: tracking progress of mental health reform in Australia 1993–2011. Canberra: Commonwealth of Australia

    Institute for Health Metrics and Evaluation (IHME) 2013. The global burden of disease: Generating Evidence, Guiding Policy. Seattle, WA: IHME, 2013. 27–29. http://www.healthmetricsandevaluation.org/gbd/visualizations/country

    Lawrence D, Johnson S, Hafekost J, Boterhoven De Haan K, Sawyer M, Ainley J, Zubrick SR 2015. The Mental Health of Children and Adolescents. Report on the second Australian Child and Adolescent Survey of Mental Health and Wellbeing. Canberra: Department of Health.

    Morgan VA, Waterreus A, Jablensky A, Mackinnon A, McGrath JJ, Carr V, et al. 2011. People living with psychotic illness 2010. Canberra: Commonwealth of Australia.