Prevalence and impact of mental illness Print this page

1 in 7 children and adolescents

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, https://heartbrides.com/latim/ 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.

There are multiple surveys which collect information on the extent of mental illness in the Australian population. This page collates evidence on the prevalence and impact of mental illness. For more information about specific surveys, refer to data sources.

How many Australians have experienced mental illness?

The following estimates come from the National Study of Mental Health and Wellbeing (NSMHW), the most robust measure of mental illness prevalence for Australia. 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 2023b).

• 8.5 million had experienced a mental disorder at some time in their life (43% of the population).
• 4.3 million had experienced a mental disorder in the previous 12 months (22% of the population; Figure 1).

• 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%) (ABS 2023a).

Figure 1: Lifetime and 12-month mental illness, by type and sex, 2020 to 2022

Figure 1.1 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 4,263,122 Australians in this age group (22% of this population) have experienced a mental disorder over the previous 12 months.

Figure 1.2 Bar chart showing the estimated proportion of Australians who reported that they have been diagnosed with a serious mental illness in the previous 12 months, by sex and age group. Figures available for 2009, 2013, 2017, 2020 and 2021. The total proportion has risen from 11% in 2009 to 19% in 2021.

Figure 1.3 Line graph showing estimated proportion of Australians who report that they have a long-term mental health condition, by sex and age group, 2003 to 2021. The total proportion of males has risen from 3% to 5% and females from 3% to 5%.

The Australian Bureau of Statistics (ABS) National Health Survey (NHS) 2020–21 provides information on a range of health conditions, including self-reported mental and behavioural disorders. The NHS records a person as having a mental or behavioural condition 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 2020–21 NHS, 1 in 5 (20%) Australians aged 15 and over were estimated to have had a mental or behavioural condition during the collection period (b).

In the 2021 Census of Population and Housing (the Census) – which includes people of all ages – over 8 million Australians (32%) reported that they had been told by a doctor or nurse that they have a long-term health condition, with 2.2 million (9%) reporting a mental health condition (including depression or anxiety) (ABS 2022a). 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).