Medical comorbidity in schizophrenia

Having a mental illness has been, and remains, a barrier to effective medical care. Schizophrenia and, indeed, most mental illnesses are associated with undue medical morbidity and mortality.1

There are two key issues relating to comorbidity: detection and prevention. In a recent article, Harris and Mercer2 discussed recommendations of the Royal Australian College of General Practitioners (RACGP)3 for preventive action in general practice. Based on loss of health calculated as age-standardised disability-adjusted life-years (DALYs),4 targets selected by the RACGP included smoking, physical activity, high blood pressure, alcohol consumption, obesity, high blood cholesterol level, diabetes, breast cancer and bowel cancer. Although all of these conditions and behaviours are known to be particularly problematic for people with schizophrenia or various other mental illnesses,1 this group, as a whole, receives less than satisfactory attention to its medical needs. The preventive role undertaken by general practitioners would be of great service to the community if it were applied more broadly to people who suffer from serious mental illness.

Schizophrenia has been described as a "life-shortening disease",5 and there is growing evidence to support this claim.6-9 Without discounting suicide, which accounts for less than a third of premature deaths, people diagnosed with schizophrenia can expect to live 9–12 years fewer, on average, than those in the general population.

Australian data support the findings of overseas studies. For example, in a study based on Victoria's Psychiatric Case Register and State coronial data, patients with schizophrenia were found to be 2.9 times more likely to die of natural causes, especially cardiovascular disease, than people in the general population.10 Studies in Western Australia1 and New South Wales7 have also shown that mortality is higher in people with schizophrenia and other mental illnesses.

It is an unfortunate situation that psychotic patients present less and are hospitalised less often for a variety of medical conditions, but are at the same time over-represented in population-matched mortality figures. This suggests that morbidity in these people is less efficiently detected.

People with schizophrenia and other mental illnesses also have high rates of physical comorbidity. However, several US studies have shown that the detection rate of physical illness among people with mental illness is very poor. Koran et al11 estimated that 45% of patients in California's public mental-health system had physical disease and, of these, 47% were undetected by the treating doctor. A substantial proportion of these illnesses were judged to be either causing or exacerbating the patient's mental illness. A study by Koranyi12 of psychiatric clinic patients revealed remarkably similar findings: 43% of patients had physical illnesses and, of these, 46% had not been diagnosed by the referring doctor (non-psychiatrist physicians had missed 33%; psychiatrists had missed 50%). Hall et al13 found that 46% of patients admitted to a research ward had an unrecognised physical illness that either caused or exacerbated their psychiatric illness; 80% had physical illnesses requiring treatment; and 4% had precancerous conditions or illnesses. Morbidity data for psychiatric populations in Australia are scant.

Illnesses that should be high in the medical practitioner's awareness are summarised in Box 1, which relates common physical illnesses to psychiatric conditions, psychotropic medications and lifestyle factors. For any individual patient, biological proneness to mental and/or physical illness is likely to interact with the patient's treatment and lifestyle. This once again reinforces the preventive notions expounded by the RACGP.3

High mortality and morbidity in schizophrenia may be attributed to an environment in which unhealthy and high-risk behaviours such as smoking, substance abuse, lack of exercise and poor diet are prevalent.31 An Australian study examining lifestyle factors that increased cardiovascular risk found significant differences between people with mental illness and the general population: 70% v 50% were smokers or ex-smokers; 11.5% v 3.1% used harmful levels of alcohol; and 40% v 8% were obese.18 The rates of obesity (body mass index [BMI] ≥ 30 kg/m2) may in fact be even higher, approaching 51% in particular groups of mentally ill patients, with a considerable number being overweight (BMI 25–29.9 kg/m2).32 Jablensky and colleagues' landmark survey of Australian low-prevalence psychotic disorders33 reported that 73% of men and 56% of women with a psychotic disorder were current smokers, while 38% of all people with a psychotic illness had been drinking daily, or for several days per week, in the year preceding the study interview. These data are consistent with overseas findings.34

Smoking-related fatalities are significantly higher in people with schizophrenia than in the general population.8 Smoking is a good example of how behaviour and treatment interact to increase morbidity at a number of levels. It is a risk factor for respiratory and ischaemic heart disease and stroke, and, by reducing available plasma levels of antipsychotics (notably olanzapine and clozapine), it may influence the patient's behaviour and the treatment outcome. With respect to diet, the cognitive and social deficit symptoms of schizophrenia may make patients prone to choosing easily obtainable "fast" foods (high in saturated fats and low in fibre) as their major source of nutrition. The same deficits, especially those to do with motivation, often leave the patient without any desire to keep physically active to counter the effects of their poor diet and maintain general fitness. This is further complicated by psychotropic side effects (particularly Parkinsonism, sedation and neuroleptic-induced cognitive deficits), which can compound these problems (see Lambert and Castle, (page 57)35). Substance misuse, a major contributor to both mortality and morbidity, and common in people with schizophrenia, is discussed by Lubman and Sundram ((page 71)).36 Together, these lifestyle factors increase the risk or severity of medical conditions, particularly the development of metabolic syndrome X (obesity, insulin resistance, dyslipidaemia, impaired glucose tolerance and hypertension).19

Barriers to effective physical healthcare for mentally ill patients include patient-related elements, the nature of the illness, the medical system and available resources, and the attitudes of medical practitioners themselves (Box 2). In community-based models of psychiatric care, as practised in Australia, it is reasonable to suggest that all members of multidisciplinary teams should receive support and training in the management of physical comorbidity, as they play a major role in influencing patients' day-to-day functioning and behaviour. Strategies that may help improve outcomes for mentally ill patients with physical comorbidity are outlined in Box 3.

Current mental health services in many parts of Australia are under-resourced for the care of people with serious mental illness. GPs are also faced with increasing responsibilities and limited support. For those with serious mental illness, an active alliance, supported by Divisions of General Practice, State and federal health departments and government policy, is needed to ensure adequate treatment and positive outcomes.