People with severe mental illnesses like schizophrenia or bipolar disorder are over three times more likely to lose their teeth because of poor oral health than the general population.

The research, published in the September issue of the British Journal of Psychiatry, shows that psychiatric patients have not shared in recent improvements in dental health.

Researchers from the University of Queensland, Australia, analysed 14 studies into the oral health of people with severe mental illness published over the last 20 years. All the psychiatric patients in the studies (2,784) had been diagnosed with severe mental illness, such as schizophrenia, dementia, bipolar disorder or other affective disorders.

The researchers found that the psychiatric patients were 3.4 times more likely to have lost all their teeth. They also had an average of 6 more decayed, filled or missing teeth than people without a psychiatric illness.

The researchers believe a combination of factors are to blame. People with severe mental illness may not be able to prioritise their oral health, or be unable to clean their teeth properly because of poor housing or homelessness. They may be reluctant to see a dentist because of they are scared of treatment, or worried about the cost. Some medications such as antidepressants and mood stabilisers can also reduce the flow of saliva and cause dry mouth (xerostomia), which increases plaque formation.

Lead researcher Professor Steve Kisely, of the University of Queensland, said:

Our analysis shows that, although the oral health of the general population has improved in much of the world, psychiatric patients remain at a disadvantage. This mirrors findings in other areas such as cardiovascular disease, where the health of the general population has improved – but not that of people with severe mental illness.

In a UK survey, the vast majority of psychiatric patients reported that clinical staff had never asked them about any dental problems. We believe that oral health should be part of the standard assessment for all patients with severe mental illness.

When patients are admitted to hospital, their care plans should include a basic assessment of oral hygiene – including factors known to cause oral ill-health such as medication, tobacco and drug use. Patients with mental illness who are treated in the community should be given advice on diet, smoking and brushing technique. We believe policy-makers should also consider providing free, accessible dental care for people with severe mental illness.

Kisely S, Quek L-H, Pais J, Lalloo R, Johnson NW and Lawrence D. Advanced dental disease in people with severe mental illness: systematic review and meta-analysis. British Journal of Psychiatry 2011; 199:187-193 [PubMed abstract]