Prevalence and impact of mental illness

Key points: In the previous 12 months over 1 in 5 (21%, or 4.2 million) Australians aged 16–85 are estimated to have experienced a mental disorder; about 1 in 6 (17%, or  3.3 million) Australians experienced an Anxiety disorder, 8% an Affective disorder and 3% a Substance Use disorder; almost 1 in 7 (14%) children and adolescents aged 4–17 years are estimated to have experienced a mental illness.

Mental health is a key component of overall health and wellbeing (WHO 2021). A mental illness can be defined as ‘a clinically diagnosable disorder that significantly interferes with a person’s cognitive, emotional or social abilities’ (COAG Health Council 2017). However, a person does not need to meet the criteria for a mental illness or mental disorder to be negatively affected by their mental health (COAG Health Council 2017; Slade et al. 2009).

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 mental illness?

The National Study of Mental Health and Wellbeing (NSMHW) is the most robust measure of mental illness prevalence for Australia. The study collected data from about 10,000 households from December 2020 to July 2021. It included an in-person interview using the World Health Organization's Composite International Diagnostic Interview, version 3.0. This instrument indicates diagnoses, rather relying on participant’s self-reporting of conditions (ABS 2022d).

Of Australians aged 16–85 in 2020–21, 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 (21% of the population; Figure 1).

The most common mental illnesses in Australia in any 12-month period are Anxiety disorders (3.3 million people or 17% of the population), Affective disorders (1.5 million or 8%) and Substance Use disorders (650,000 or 3%) (ABS 2022c).

Figure 1: Estimated number of Australians aged 16–85 experiencing mental illness by time period and disorder, 2021

Figure 1: Bar chart showing the estimated number of male and female Australians aged between 16 and 85 experiencing any of 12 mental disorders, either over their lifetime or in the previous 12 months. An estimated 8,589,100 Australians in this age group (43.7% of this population) have experienced a mental disorder in their lives.

Source: National Study of Mental Health and Wellbeing, 2021

Measuring mental illness

There are multiple surveys which collect information on the extent of mental illness in the Australian population. The aim is to provide evidence on the prevalence of mental illness, disability associated with mental illness, and the use of health and other services by people experiencing mental illness.

How common is mental illness among Australian adults?

Over 2 in 5 (44%) Australians aged 16–85 were estimated to experience a mental illness at some time in their life (about 8.6 million people), according to the NSMHW 2020–21. It is also estimated that over 1 in 5 people (21%) experienced a mental disorder in the previous 12 months (about 4.2 million people). 

Of these:

  • Anxiety disorders (such as Social phobia) were the most common, affecting 1 in 6 (17%) Australians
  • Affective disorders (such as Depressive episode) (8%)
  • Substance Use disorders (such as Alcohol dependence) (3%) (ABS 2022c).

The Australian Bureau of Statistics (ABS) National Health Survey (NHS) 2020–21 provides information on a range of health conditions, including mental and behavioural disorders. The NHS estimates are based on self-reported information and records a person as having a mental or behavioural condition during the collection period only if the condition was reported as long-term (had lasted, or was expected to last 6 months or longer). The NHS 2020–21, estimated that 1 in 5 (20%) Australians reported that they had a mental or behavioural condition during the collection period (August 2020 to June 2021) (ABS 2022b). 

How common is mental illness among Australian children and adolescents?

The second national survey of the mental health and wellbeing of Australian children and adolescents was undertaken in 2013–14, with almost 3,000 people aged 4–17 participating. The survey included a structured diagnostic interview to assess young people against mental disorder criteria (Lawrence et al. 2015).

From this survey, almost 1 in 7 (14%) children and adolescents aged 4–17 years were estimated to have experienced mental illness in the previous 12 months, which is equivalent to about 628,000 people (based on the estimated 2022 population). The most common mental illnesses among children and adolescents were:

  • Attention Deficit Hyperactivity Disorder (7%, or about 334,000 people)
  • Anxiety disorders (7%, or about 312,000)
  • Major depressive disorder (3%, or about 126,000)
  • Conduct disorder (2%, or about 95,000).

Almost one third (30%) of adolescents with a mental illness experienced 2 or more mental illnesses at some time in the previous 12 months.

Male children and adolescents (16%) were more likely than females (12%) to have experienced mental illness in the previous 12 months. The prevalence of mental illness was slightly higher for older females (13% for those aged 12–17) than for younger females (11% for those aged 4–11). However, the prevalence for males did not differ markedly between the younger and older age groups (17% and 16% respectively) (Lawrence et al. 2015).

How many Australians are living with psychotic illness?

Mental illness includes conditions with low prevalence and severe consequences, including psychotic illnesses (DoHA 2010). Psychotic illnesses may be characterised by symptoms including disordered thinking, hallucinations, delusions and disordered behaviour, and include Schizophrenia, Schizoaffective disorder and Delusional disorder. 

The 2010 National Psychosis Survey estimated that 64,000 Australians aged 18–64 experienced a psychotic illness and were in contact with public specialised mental health services each year. This equates to 5 cases per 1,000 population. The survey found the most frequently recorded of these disorders was Schizophrenia which accounted for almost half of all diagnoses (47%) (Morgan et al. 2011).

How many Australians experience psychological distress?

What is psychological distress?

Another insight into the mental health and wellbeing of Australians is provided by measures of psychological distress, which may include nervousness, agitation, psychological fatigue and depression. 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 regarding 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 anxiety 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 the presence of mental illness. 

Surveys which measure psychological distress include the National Study of Mental Health and Wellbeing, the National Health Survey and the Household, Income and Labour Dynamics in Australia (HILDA) survey.

Among Australians aged 16–85, as measured from late 2020 to mid 2021, 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 with 14%) (Figure 2) (ABS 2022c). For more information on psychological distress, see the AIHW suicide and self-harm monitoring site.

Figure 2: Estimated number of Australians aged 16–85 experiencing psychological distress, 2021

Figure 2: Bar chart showing the estimated number of male and female Australians aged between 16 and 85 experiencing high or very high psychological distress, either by disorder group or age group. An estimated 1,218,100 Australian females living with one or more mental disorder (65.5% of this population) experienced high or very high psychological distress. 

Source: National Study of Mental Health and Wellbeing, 2021; National Health Survey 2011–12, 2020–21

Impact of mental illness on population groups

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

2021 Census

The Census of Population and Housing (the Census) is undertaken every 5 years and aims to collect data from every person and household in Australia. In 2021, the Census included new questions on 10 common long-term health conditions. 

Over 8 million Australians (about 32%) reported that they had been told by a doctor or nurse that they have a long-term health condition, with 2.2 million (about 9%) reporting a mental health condition (including depression or anxiety) (ABS 2022a). Some insights gleaned from the Census include:

  • About 11% of people who usually reside in Tasmania have been told by a doctor or nurse that they have a mental health condition, this highest proportion of any state or territory.
  • Double the proportion of females aged 20–29 report a mental health condition compared to males the same age (16% and 8%, respectively)
  • People who have no usual address tend to report a higher proportion of mental health conditions than people usually residing in fixed geographic areas (Figure 3).

Although the Census provides valuable information, the ABS recommends that the NSMHW be used as the reference source for mental illness prevalence data as it uses diagnostic criteria, rather than the self-reporting approach used in the Census and other surveys (ABS 2022c). For more information, see Comparing ABS long-term health conditions data sources.

Figure 3: Census data by states and territories, SA4 and PHN

Figure 3: Interactive data visualisation comparing reported mental illness between states and territories, Primary Health Networks and statistical areas.

AIHW analysis of Australian Bureau of Statistics (2022) Census TableBuilder

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. One in 5 (21%) Australians experience mental illness in any given year, according to the NSMHW. In most cases, the impact on the individual will be mild (9%, or an estimated 1.4 million people) or moderate (5%, or an estimated 710,000 people). It is estimated that around 3% or 500,000 people have a severe mental illness, of which 330,000 people have episodic mental illness and 170,000 have persistent mental illness (Whiteford et al. 2017).

Burden of disease

Mental and substance use disorders, such as Depression, Anxiety and Drug use, are substantial components of overall disability and morbidity. The Australian Burden of Disease Study 2022 examined the health loss due to disease and injury after treatment, rehabilitative and preventative efforts of the health system and society. For Australia, Mental and substance use disorders were estimated to be responsible for 12% of the total burden of disease, placing it fourth as a broad disease group after Cancer (17%), Musculoskeletal conditions (13%) and Cardiovascular diseases (12%) (AIHW 2022).

Where do I go for more information?

For more information, refer to:

Data sources

Key concepts

Key concept


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).

Episodic mental illness

An episodic mental illness is characterised by acute episodes of symptoms, which may be severe and disabling, with periods of minimal symptoms or remission.

Persistent mental illness

In persistent mental illness, the severity and impact of symptoms may fluctuate but remain chronic and may be disabling.


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).