Physical health of people with mental illness

Key points

People living with mental illness, and in particular severe mental illness (SMI), are more likely to experience comorbidity of physical conditions, more likely to be hospitalised for potentially preventable reasons and tend to die earlier than the general population (Sara et al. 2021; Lawrence et al. 2013).

For more information on mental illness, see the Prevalence and impact of mental illness.

How common is physical illness among people with mental illness?

According to the 2020–2022 NSMHW, an estimated 4.3 million Australians aged 16–85, or 22% of this population, had experienced a mental disorder in the 12 months prior to the study. Of these, 39% also had a long-term physical health condition. This represents an estimated 1.7 million people, or 8% of adults, experiencing both a mental illness and a long-term physical health condition (ABS 2023).

The 2021 Census results – which include people of all ages – found that people who reported having a mental illness were more likely to report also having another long-term health condition (Figure 1; ABS 2022b). Among the most common long-term conditions reported by those with a mental illness were arthritis, asthma and diabetes (Figure 1). Given the Census relies on people self-reporting long-term conditions, this is likely to be an underestimate as many people did not respond to this item, may not be aware that they have a long-term health condition or their mental illness did not satisfy the requirements of being considered long-term (that is, lasting 6 months or longer). For more information, view Chronic conditions and Multimorbidity.

A recent study of Australian general practice records examined the prevalence of physical health conditions and biomedical risk factors among people with severe mental illness (Belcher et al. 2021). Similarly, it showed a notable overlap between mental and physical illnesses. The prevalence of all surveyed biomedical risk factors was higher among patients with SMI than patients without. These included:

• dyslipidaemia (high cholesterol) (25% among those with SMI compared with 18% in patients without)
• hypertension (27% compared with 22%)
• obesity (29% compared with 19%).

The prevalence of all surveyed physical conditions was also higher among patients with SMI than patients without. These included:

• back pain (35% among those with SMI compared with 19% in patients without)
• cardiovascular disease (10% compared with 6.7%)
• gastro-oesophageal reflux disease (29% compared with 15%)
• arthritis (27% compared with 19%)
• cancer (19% compared with 15%).

Almost three-quarters (71%) of patients with SMI had at least one of the surveyed physical health conditions, compared with 54% of people without.

The second National Survey of People Living with Psychotic Illness includes estimates on the physical health of Australians living with a psychotic illness (Morgan et al. 2012). The prevalence of several physical conditions was higher among people with psychotic illness than people without. These included:

• chronic back, neck or other pain (32% among those with psychotic illness compared with 28% for the general population)
• asthma (30% compared with 20%)
• heart or circulatory conditions (27% compared with 16%).

In 2010, 24% of people with a psychotic illness were at high risk of cardiovascular disease, 45% were obese and 38% reported gaining weight as a medication side effect. Physical activity levels were markedly lower in people with a psychotic illness, with 96% classified as either sedentary or undertaking low levels of exercise in the previous week compared with 72% for the general population (Morgan et al. 2012).

Causes of physical illness among people with mental illness

Mental health is known to affect physical health and vice versa (Doan et al. 2023). For example, there is a long-established association between depression and heart disease. Multiple studies across various populations have shown that people with depression but no history of heart disease when the depression is assessed, are at markedly higher risk for coronary heart disease or cardiac mortality (Carney and Freedland 2003). Similarly, among patients who have just experienced a major cardiac event, such as a heart attack, those with depression are at an increased risk of another cardiac event or cardiac mortality compared to those without depression (Dhar and Barton 2016).

While the association between depression and coronary heart disease is well known, researchers have only recently begun to understand the biological mechanisms behind this relationship (Dhar and Barton 2016). Poor mental health can inhibit physical health behaviours – for example, it can lead to reduced physical activity or substance use as people try to self-medicate the symptoms of mental illness or psychological distress. Yet the reasons people with mental illness and especially SMI are more likely to experience poorer physical health and reduced life expectancy compared to the general population go beyond these mechanisms.

According to the Royal Australian and New Zealand College of Psychiatrists, the reasons people living with severe mental illness experience poorer physical health include:

• greater exposure to the known risk factors for physical disease such as lower socio-economic status, smoking, poor nutrition, reduced physical activity and higher sedentary behaviour
• reduced access to and quality of health care due to financial barriers, and stigma and discrimination among health care providers
• systemic issues in health care delivery, especially the separation of mental and physical health services, and a lack of clarity about who is responsible for monitoring the physical health of people with serious mental illness
• adverse effects of psychotropic medication, in particular their contribution to metabolic syndrome, obesity, cardiovascular disease and type 2 diabetes
• impacts from polypharmacy (the prescription of multiple medications) and prescribing practices
• lack of capability among both generalist and specialist health care staff to deal with complex comorbidities – mental health staff may lack skills, training and confidence to treat physical conditions and vice versa for physical health teams (RANZCP 2015).

For some people living with mental illness, symptoms may interfere with receiving medical care or compromise effective communication of physical symptoms with health care workers (Melamed et al. 2019).

In addition to poorer physical health and shorter life expectancy, higher rates of physical comorbidity among people with SMI can lead to higher levels of ongoing disability, reduced participation in the workforce and a greater likelihood of poverty and welfare dependency (RANZCP 2015).

Life expectancy

Studies suggest that globally, the life expectancy of people with a mental illness is reduced compared with the general population (Chang et al. 2011; Momen et al. 2022; Plana-Ripoll et al. 2019; Walker et al. 2015). Research from Western Australia found that the gap in life expectancy for people with mental illness registered with West Australian mental health services compared with the general population in 2005 was 15.9 years for men and 12.0 years for women (Lawrence et al. 2013).

This research also indicated that the mortality gap for people living with mental illness had increased by 2.5 years for men and 1.6 years for women from 1985, with the increase largely driven by gains in life expectancy for the general population (Lawrence et al. 2013). This finding aligns with studies from other high-income countries suggesting that the mortality gap for people with mental illness may be increasing over time, in part due to gains in life expectancy for the general population not experienced (or at least not experienced in equal measure) by those with mental illness and especially SMI (Hayes et al. 2017; Laursen et al. 2019; Momen et al. 2022).

It is estimated that almost 80% of premature deaths of people with mental illness are due to potentially preventable physical health comorbidities such as type 2 diabetes, respiratory diseases, cancer and cardiovascular disease rather than as a direct result of mental illness or death by suicide (Lawrence et al. 2013). Compared with the general population, people with SMI have a 2- to 3-fold risk of developing hypertension and metabolic syndrome and, if under the age of 50, a 3-fold risk of dying from coronary heart disease (De Hert et al. 2009; Osborn et al. 2007). Furthermore, studies suggest that people who live with SMI and receive a cancer diagnosis experience higher rates of mortality compared to the general population (Charlesworth et al. 2023; Launders et al. 2022).

Substance use disorder is particularly associated with reduced life expectancy. A recent study has shown that substance use disorder has a profound negative impact on mortality and years of life lost following the onset of comorbid physical health conditions when compared with people with the same physical conditions, but no history of substance use disorder (Formanek et al. 2022). In 26 of the 28 physical health conditions surveyed, people with a history of hospitalisation for substance use disorder were more likely to die than their counterparts without this history (Formanek et al. 2022). People with mental illness are known to be at increased risk of premature mortality, but among all mental illness types, substance use disorder has been associated with the highest number of years of life lost (YLL) (Plana-Ripoll et al. 2019).

While mental illness is associated with poorer health outcomes and a reduced life expectancy, comorbid substance use disorder alongside other mental disorders is associated with markedly higher mortality rates and larger reductions in life expectancy (Plana-Ripoll et al. 2020). For more information on comorbidity of substance use disorders and other mental illness, view Mental health and substance use.

Future directions

Data linkage, for example through the National Health Data Hub may provide further insights into the relationships between mental illness, physical comorbidities and mortality among the Australian population. While separate data collections provide a limited view on peoples’ overall health, data linkage allows for analysis of the impact of mental illness on physical health conditions from across different service settings and types of service usage. This data could assist in identifying areas of disadvantage in broader health settings and barriers to service usage for people with mental illness, which is critical as this population group accesses health services at a lower rate than the general population.

Where can I find more information?

For more information on the physical health of people with mental illness, see:

• Equally Well: Improving the physical health of people living with mental illness
• Victoria University: Being equally well roadmap
• The Royal Australian & New Zealand College of Psychiatrists: Expert consensus statement for the treatment, management and monitoring of the physical health of people with an enduring psychotic illness
• Mental health and substance use