Prevalence and impact of mental illness

Key points

In a 12-month period, an estimated...

Mental health is a term that is used to describe both the positive and negative mental states of individuals, often described as mental well-being or mental illness. The World Health Organization defines mental well-being as a state “that enables people to cope with the stresses of life, realize their abilities, learn well and work well, and contribute to their community” (WHO 2025). 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 to be negatively affected by their mental health.

There are a number of surveys which collect information on different aspects of the extent of mental illness in the Australian population. This page collates evidence on the prevalence and impact of mental illness. The estimated population rate of mental illness in Australia can vary depending on what data source is used, how recent this has been collected, what instruments and measures have been used in the survey and the criteria for reporting as having a mental illness. There are several informative studies that can be used to report on the prevalence of mental illness in Australia. For more information about specific surveys, refer to data sources.

The terms ‘mental illness’, ‘mental disorder’, ‘mental health condition’, ‘psychiatric illness’ and other terms are used across a range of different studies and data sources to describe a range of mental health and behavioural disorders, which can vary in both severity and duration. For this page, the term mental illness is used for consistency.

How many Australians have experienced mental illness?

The most comprehensive insights into the prevalence of mental illness in Australia is the 2020–2022 National Study of Mental Health and Wellbeing (NSMHW). The study provides unique data by utilising the World Health Organization’s Composite International Diagnostic Interview (version 3.0) which is an instrument that indicates diagnosis, rather than relying on participant’s self-report of mental illness (ABS 2023d). For further information about the study parameters, see National Health Survey methodology, 2022.

The NSMHW estimates that 22% of the population (4.3 million people) aged 16–85 had experienced a mental illness in the previous 12 months, while 43% of the population (8.5 million people) had experienced a mental illness during their life.

In the 12 months prior to the study, the most common mental illnesses in Australia were:

• Anxiety disorders (3.4 million people, or 17% of the population)
• Affective disorders (1.5 million, or 8%)
• Substance Use disorders (650,000, or 3%) (Figure 1, ABS 2023e).

The most recent Australian Child and Adolescent Survey of Mental Health and Wellbeing, also referred to as the Young Minds Matter Survey, was conducted in 2013–14. Almost 3,000 people aged 4–17 participated, and the survey included a structured diagnostic interview to assess young people against mental illness criteria (Lawrence et al. 2015). The survey estimated that 14% of children and adolescents aged 4–17 have a mental illness.

The 2010 Survey of High Impact Psychosis (SHIP) is Australia’s 2nd national psychosis survey which provides estimates on the prevalence of psychotic illness in Australia. Psychotic illnesses may be characterised by symptoms including disordered thinking, hallucinations, delusions and disordered behaviour and include diagnoses like schizophrenia, schizoaffective disorder and delusional disorder. The SHIP estimated that in 2010 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 Schizophrenia accounted for almost half (47%) of all psychotic illness diagnosis (Morgan et al. 2011).

The 2021 Australian Bureau of Statistics (ABS) Census of Population and Housing (the Census) included a question about long-term health conditions for the first time. The aim of the question was to explore the prevalence of long-term health conditions in relation to other variables collected, such as demographic and socioeconomic characteristics, where people live, household composition and cultural and linguistic diversity. In 2021, 32% of respondents (over 8 million people) reported having at least one long-term health condition. Of the 10 long-term health conditions included in the survey, mental illness reported the highest rate and is estimated to affect 8.8% of the population (ABS 2023a).

The ABS National Health Survey (NHS) 2022 provides information on a range of health conditions, including self-reported mental illness. The NHS records a person as having a mental illness during the collection period only if the person reports that the condition had lasted, or was expected to last, 6 months or longer. According to the 2022 NHS, 26% of Australians aged 15 and over were estimated to have a mental illness during the collection period (January 2022 to April 2023) (ABS 2023a).

The Household Income Labour Dynamics in Australia (HILDA) is a household-based panel hosted by the University of Melbourne. The study collects valuable information about economic and personal well-being, labour market dynamics and family life. Results from the 2021 HILDA survey estimate that 19% of the population reported receiving a serious mental illness diagnosis during their life and 6% of the population reported having a long-term mental illness (Figure1, Wilkins et al. 2024).

Changes to the mental health of Australians over time

The NSMHW provides the best estimate for changes to the prevalence of mental illness in Australia. The study has been conducted 3 times, first in 1997 (ABS 1998), 2007 (ABS 2008) and most recently in 2020–2022 (ABS 2023e). The NSMHW assessed 3 groups of mental disorders: Anxiety, Affective and Substance Use disorders. Both the 2020–2022 and 2007 surveys asked respondents about their experiences and symptoms of mental ill-health throughout their lifetime, from which lifetime mental disorders and 12-month mental disorders were analysed.

Estimates from the 2 surveys showed only minor differences in the overall prevalence of mental illness among the Australian population:

• There was a slight decrease in the proportion of people aged 16–85 reporting a lifetime mental illness, from 45% in 2007 compared with 43% in 2020–2022.
• Conversely, there was a slight increase in the proportion of people reporting having a 12-month mental disorder, from 20% in 2007 compared with 22% in 2020–2022.
• The prevalence of a 12-month mental disorder among males remained stable at 18% in 2007 and 2020–2022, while females reported a slight increase from 22% in 2007 to 25% in 2020–2022.

While the prevalence of a 12-month mental disorder remained broadly similar between the 2007 and 2020–2022 surveys for people aged 25–85, there was an increase in prevalence among young adults. For those aged 16–24:

• 26% reported a 12-month mental disorder in 2007 compared with 39% in 2020–2022.
• Females reported a slightly higher increase in prevalence with 30% reporting a 12-month mental disorder in 2007 compared with 46% in 2020–2022.
• Comparatively, males reported a smaller increase in prevalence with 23% reporting a 12-month mental disorder in 2007 compared with 32% in 2020–2022.

Changes in methodology and diagnostic criteria mean that some comparisons between the 2007 and 2020–2022 studies should be made with caution. For more information, see Data interpretation.

Age and sex

The prevalence of mental illness in Australia varies by age and sex demographics. In 2021, the proportion of females aged 20–29 (16%) that reported being told by a doctor or nurse that they have a mental illness was double that of males in the same age group (8%) (ABS 2022b).

In 2021, the estimated prevalence of depression or anxiety was highest among younger women and men (aged 15–34) at 22%, compared with 15% for people aged 55 and over (ABS 2022b). Since 2017, depression or anxiety prevalence rates exceeded asthma as the most common serious illness for this age group (Figure 2).

These data mirror the trends shown by the NSMHW, however there is some disparity between the reported percentages. This is due to a range of factors such as different study methodologies, different criteria for reporting a mental illness and the studies being conducted at different times (ABS 2022a).

Persistence of mental illness

The HILDA survey collects additional health information every 4 years which allows the persistence of serious illness to be considered. The 2021 survey results showed that of those who reported having depression or anxiety in 2017:

• 61% of males reported still having the condition 4 years later.
• 71% of females reported still having the condition 4 years later.
• 70% of people aged 15–34 reported still having the condition 4 years later.
• 69% of people aged 35–54 reported still having the condition 4 years later.
• 64% of people aged 55 and over reported reported still having the condition 4 years later (Wilkins et al. 2024).

In addition, of those who accessed treatment for their depression or anxiety diagnosis in 2017:

• 74% reported still having the condition 4 years later.
• 9% reported not having the condition but having other serious illnesses 4 years later.
• 17% reported not having any serious illness 4 years later.

Similarly, of those who took prescribed medication for their depression or anxiety diagnosis in 2017:

• 76% reported still having the condition 4 years later.
• 18% reported not having the condition but having other serious illness 4 years later.
• 6% reported not having any serious illness 4 years later.
  
  

Children and adolescents

About 14% of children and adolescents aged 4–17 were estimated to have experienced mental illness in the previous 12 months. The most common mental illnesses among children and adolescents were:

• Attention Deficit Hyperactivity Disorder (7%)
• Anxiety disorders (7%)
• Major depressive disorder (3%)
• Conduct disorder (2%).

About 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 younger (11% for those aged 4–11). The prevalence for males did not differ markedly between the younger and older age groups (17% and 16%, respectively) (Lawrence et al. 2015).

In 2021, HILDA estimates showed that around 7% of Australians aged 15–17 had a long-term mental health condition such as a nervous or emotional condition which requires treatment, or a mental illness which requires help or supervision. This proportion has increased from 2% in 2003. In addition, 19% of Australians in this age group were estimated to be diagnosed with depression, anxiety or any other mental illness, an increase from 6% in 2009 (Wilkins et al. 2024).

Based on the 2021 HILDA survey, more adolescents reported frequently feeling ‘so down in the dumps nothing could cheer you up’ compared with 2008. The average score for this question has decreased from a high of 5.3 in 2008 to a low of 4.7 in 2021. The average score reporting how often adolescence ‘felt calm and peaceful’ has increased from 2.8 to 3.2, indicating that fewer adolescents report feeling calm and peaceful frequently (Figure 4, Wilkins et al. 2024).

How does mental health differ across Australia?

Data from the 2021 Census provide insights into the prevalence of mental illness in Australia by characteristics. People who do not have a usual address reported a higher proportion of mental illness than people who do have a usual address (Figure 5). People with no usual address in Tasmania, Australian Capital Territory, South Australia, Victoria, New South Wales and Queensland reported the highest rates of mental illness in the state. Tasmania reported the highest proportion of people in any state or territory that had been told by a doctor or a nurse they have a mental illness (11% of people who usually reside in Tasmania) while the Northern Territory reported the lowest proportion (5% of people who usually reside in the Northern Territory).

How many Australians experience psychological distress?

Another insight into the mental health and wellbeing of Australians is provided by measuring psychological distress in the population. Signs of psychological distress may include symptoms such as nervousness, agitation, psychological fatigue and depression. The 2020–2022 NSMHW estimated that 17% of Australians aged 16–85 experienced high or very high levels of psychological distress. The study also found that among younger people aged 16–24, females were more likely to experience psychological distress (34%) than males (18%) (Figure 6).

Psychological distress is commonly measured using the Kessler 10 Psychological Distress Scale (K10), which asks questions regarding negative emotional states which may have been experienced in the past 30 days (ABS 2023c). It is important to note that someone who is experiencing psychological distress will not necessarily be experiencing mental illness, however there is a strong correlation between high scores on the K10 and the presence of depressive or anxiety disorders (Lawrence et al. 2015). As the K10 is an established and relatively effective means of measuring psychological distress, high and very high levels of psychological distress are often used as a proxy for the presence of mental illness.

Impact of mental illness

The HILDA survey collects information on the extent to which health conditions impact an individual’s everyday activities. In 2021, for people who reported having a long-term mental illness, an estimated:

• 17% reported needing help or supervision due to their condition.
• 59% of people aged under 65 reported having difficulties with employment due to their condition. These difficulties included needing ongoing assistance or special equipment to work, having to restrict number of work hours or type of work they can do, among others.
• 58% of students aged under 65 had difficulties with education due to their condition (Wilkins et al. 2024).

HILDA also collects information on the degree to which health conditions limit the amount of work an individual can do (on a scale of 0 to 10, where 0 equals ‘not at all’ and 10 equals ‘unable to do any work’). In 2021, an estimated 68% of people reported that their condition limits the type or amount of work they can do, of these, about half reported a score higher or equal to 7, with 12% scoring 10.

Burden of mental illness

Severity

Mental illness affects many Australians, either directly, for those who experience it or indirectly, such as family members, friends and carers. Mental illness can vary in severity and be episodic or persistent in nature. In most cases, the impact on the individual will be mild (7%) or moderate (9%). It is estimated that around 7% have a severe mental illness (ABS 2023d: Table 2).

Burden of disease

Mental health conditions and substance use disorders, such as Depression, Anxiety and Drug use, are substantial components of overall disability and morbidity in Australia. The ABS National Health Survey methodology measures the impact of diseases and injuries on a population. Mental and substance use disorders were estimated to be responsible for 15% of the total burden of disease, placing it second as a broad disease group after Cancer (17%) (AIHW 2024b).

Impact of illicit drugs

There is a complex relationship between mental health and alcohol and other drug use. A mental illness may make a person more likely to use drugs to provide short-term relief from their symptoms, while other people have drug problems that may trigger the first symptoms of mental illness (AIHW 2024a). It is often difficult to determine whether mental illness preceded substance use or vice versa.

According to the 2022–2023 National Drug Strategy Household Survey:

• between 2019 and 2022–2023 there was an increase in the proportion of people who had recently used an illicit drug (in the past 12 months) experiencing high or very high levels of psychological distress (from 26% to 30%) (AIHW 2024a: Table 10.17)
• the proportion of people who recently used an illicit drug and had been diagnosed with or treated for a mental health condition in the previous 12 months remained stable from 26% in 2019 to 29% in 2022–2023 (AIHW 2024a: Table 10.19).

Disease expenditure

The Health system spending on disease and injury in Australia 2022–23 report provides estimates of Australia’s national health spending. In 2022–23, expenditure on Mental health conditions and substance use disorders accounted for almost 7% ($11.9 billion) of total spending by broad disease groups. Of these:

• over half (52%) of total spending was on public hospitals, totalling $6.1 billion
• public hospital admitted patient has consistently been the highest area of spending, increasing from $2.7 billion in 2013–14 to $4.8 billion in 2022–23 in real terms (AIHW 2024c).

In 2024, Mental health conditions and substance use disorders as a broad disease group accounted for almost 15% of the burden of disease in Australia (AIHW 2024b). For more in-depth analysis about expenditure on mental health, refer to Expenditure on mental health services.

Where can I find more information?

For more information on the prevalence of mental illness, see:

• ABS National Health Survey methodology
• Stress and trauma
• Australian Bureau of Statistics (ABS), Census of Population and Housing 2021
• ABS National Health Survey methodology
• ABS National Study of Mental Health and Wellbeing
• The University of Melbourne, Household, Income and Labour Dynamics in Australia

Data interpretation

Data sources