Prevalence and impact of mental illness

Summary

Key points

  • Over 2 in 5 (44%, or 8.6 million) Australians aged 16–85 are estimated to have experienced a mental disorder at some time in their life, with 1 in 5 (21%, or 4.2 million) having experienced a mental disorder in the previous 12 months.
  • Anxiety disorders (such as Social Phobia) are the most common type of disorder, affecting 1 in 6 (17%, or 3.3 million) Australians, followed by Affective disorders (such as Depressive Episode) (8%), and Substance Use disorders (such as Alcohol Dependence) (3.%).
  • Almost 1 in 7 (14%) children and adolescents aged 4–17 years are estimated to have experienced a mental illness in the previous 12 months.
  • 5% or 800,000 people are estimated to have a severe mental illness, of which 500,000 people have episodic mental illness and 300,000 have persistent mental illness.
  • Mental and substance use disorders were the second largest contributor (24%) of the non-fatal burden of disease in Australia.

Mental health is a key component of overall health and wellbeing (WHO 2021). A mental illness refers to a clinically significant disturbance in an individual's cognition, emotional regulation, or behaviour, usually associated with distress or impairment in important areas of functioning (WHO 2022).

On this page the terms ‘mental illness’ and ‘mental disorder’ are both used to describe a range of mental health and behavioural disorders, which can vary in both severity and duration.

How many Australians have experienced a mental disorder?

Of Australians aged 16–85, an estimated:

  • 8.6 million have experienced a mental disorder at some time in their life (44% of the population).
  • 4.2 million have experienced a mental disorder in the previous 12 months.

The most common mental illnesses in Australia are Anxiety Disorders, Affective Disorders (such as Depression) and Substance use disorders (ABS 2022a).

FIgure 1. Estimated number of Australians aged 16-85 experiencing mental illness by time period and disorder, 2021

Figure showing the number of different mental health disorder by males and females during a lifetime and during a 12 month period. This figures also shows to the number of males and femails with high or very high psychological distress by disorder group and by age group.

Notes

  1. Estimates of Alcohol Dependence and Drug Use Disorders have a relative standard error of 25% to 50% and should be interpreted with caution.
  2. Refer to National Study of Mental Health and Wellbeing methodology, 2020-21 | Australian Bureau of Statistics (abs.gov.au) for more information.
  3. Some estimates have a relative standard error greater than 25% and should be interpreted with caution. Refer to National Study of Mental Health and Wellbeing methodology, 2020-21 | Australian Bureau of Statistics (abs.gov.au) for more information.

Source: Australian Bureau of Statistics, National Study of Mental Health and Wellbeing: Summary Results, 2020–21; Tables 1.1, 1.3, 2.1, 2.3, 5.1, 5.3, 14.1, 14.3.

Prevalence

A program of surveys, the National Survey of Mental Health and Wellbeing (NSMHWB), began in Australia in the late 1990s. The role of these surveys is to provide evidence on the prevalence of mental illness in the Australian population, the amount of disability associated with mental illness, and the use of health services by people experiencing mental illness. These surveys have 3 main components—a population-based survey of adults, a service-based survey of people with psychotic disorders, and a population-based survey of children.

How many Australians experience psychological distress?

Another insight into the mental health and wellbeing of Australians is provided by measures of psychological distress. Psychological distress can be described as unpleasant feelings or emotions that affect a person’s level of functioning and interfere with the activities of daily living. This distress can result in having negative views of the environment, others and oneself, and manifest as symptoms of mental illness, including anxiety and depression.

How is psychological distress measured?

Psychological distress is commonly measured using the Kessler 10 Psychological Distress Scale (K10) a scale based on questions about negative emotional states experienced in the past 30 days (ABS 2012). Someone experiencing psychological distress will not necessarily be experiencing mental illness, although high scores on the K10 are strongly correlated with the presence of depressive or anxious disorders (Andrews and Slade 2001). As it is relatively straightforward to measure, ‘high’ and ‘very high’ levels of psychological distress are often used as a ‘proxy’ for mental illness.

In additional to mental disorder prevalence, the 2020–21 NSMHWB also measured psychological distress. It found that, among Australians aged 16–85, 15% experienced high or very high levels of psychological distress. Females aged 16–34 were more likely to experience psychological distress than males of this age group (26% compared to 14%) (ABS 2022a). Refer to the data visualisation for more detail.

Psychological distress and COVID-19

In the longitudinal study, COVID-19 Impact Monitoring Survey Program, researchers from the Australian National University found a substantial increase in the levels of psychological distress between February 2017 and April 2020, the equivalent of an increase of 8% to 11% of people reporting a serious mental illness. Increases in psychological distress were seen particularly for young Australian adults, with the proportion of people aged 18–24 experiencing high levels of psychological distress increasing from 14% in 2017 to 22% in April 2020 (Biddle et al. 2020).

Over the course of the pandemic, psychological distress has fluctuated, reaching highs in April 2020, October 2020 and October 2021. As of January 2022, psychological distress remained elevated compared to February 2017 (Biddle and Gray 2022).

Impact of mental illness on population groups

It is recognised that some groups experience higher rates of mental illness and psychological distress than others.

Impact and burden of mental illness

Mental illness affects all Australians either directly or indirectly. Mental illness can vary in severity and be episodic or persistent in nature. An estimated 1 in 5 Australians experience mental illness in any given year, most of which will be mild (15% or an estimated 2.3 million Australians among the 15.3 million Australians) or moderate (7%, or an estimated 1.2 million people). It is estimated that around 5% or 800,000 people have a severe mental illness, of which 500,000 people have episodic mental illness and 300,000 have persistent mental illness (Productivity Commission 2020).

Burden of disease

Mental and substance use disorders, such as Depression, Anxiety and Drug use, are important drivers of disability and morbidity. The most recent Australian Burden of Disease Study (2018) 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. For Australia, Mental and substance use disorders were estimated to be responsible for 13% of the total burden of disease in 2015, placing it 4th as a broad disease group after Cancer (18%), Musculoskeletal conditions (13%) and Cardiovascular diseases (14%) (AIHW 2021).

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 substance use disorders were the 2nd largest contributor (24%) of the non-fatal burden of disease in Australia, behind Musculoskeletal conditions (25%) (AIHW 2021).

Comorbidity

There is an association between diagnosis of mental illness and a physical disorder, often referred to as a ‘comorbid' disorder. From the 2007 NSMHWB of adults, 1 in 8 (12%) of people with a 12-month mental illness also reported a physical condition, with 1 in 20 (5%) reporting 2 or more physical conditions (ABS 2008).

According to the 2010 National Psychosis Survey, people with a psychotic illness also frequently experience poor physical health outcomes and comorbidities. For example, over one-quarter (27%) of survey participants had heart or circulatory conditions and over one-fifth (21%) had diabetes (compared with 16% and 6% respectively in the general population). This prevalence of Diabetes is more than 3 times the rate seen in the general population. Other comorbidities included Epilepsy (7% compared with 1% in the general population) and Severe headaches/migraines (25% compared with 9% in the general population) (Morgan et al. 2011).

Where do I go for more information?

More information on mental health can be found at:

Key concepts
Key concept Description
Burden of disease Burden of disease is measured in disability-adjusted life years (DALYs)—years of life lost due to premature mortality (fatal burden) and years of healthy life lost due to poor health (non-fatal burden).
Comorbidity Comorbidity refers to occurrence of more than 1 condition/disorder at the same time.
Prevalence Prevalence measures the proportion of a population with a particular condition during a specified period of time (period/point prevalence), usually measured over a 12-month period or over the lifetime of an individual (lifetime prevalence).