Reporting their findings in the journal PlosOne, four mental health researchers in Queensland analyzed data collected in the Australian National Survey of Health and Wellbeing. They identified Australians who reported mental health issues associated with schizophrenia (except hallucinations, which were not asked about in the survey). These could be people who reported feelings of persecution, feelings of anxiety, or statements of "magical thinking," such as rubbing crocodile teeth against bananas to make them grow because crocodile teeth are shaped like bananas and are very strong. The researchers then linked the frequency of these mental health markers to a variety of chronic health conditions including diabetes.
- 21% of Australians who had cardiovascular disease reported delusion-like experiences,
- 20% of Australians who had asthma or arthritis reported delusion-like experiences, and
- 8% of Australians who had diabetes or cancer reported delusion-like experiences.
When the researchers accounted for social status, economic status, unfamiliarity with the English language, recency of immigration to Australia, sex, and age, they still found that a significant number of Australians who had these chronic health conditions also suffered a psychological issue. The question the survey could not answer is whether the health problems caused psychological distress or whether the treatment for the health problems caused psychological distress. After all,
- Beta-blockers are still common in treatment of heart disease, and are known to cause depression.
- Steroid drugs are often used to treat asthma and arthritis, and can cause psychological disturbances.
- Considerably more than 8% of diabetics are treated with insulin, and taking too much or too little insulin can have a profound effect on mental status.
And at least in this study, psychological issues were less common among diabetics than among Australians with other chronic diseases.
The World Health Organization estimates that up to 14% of the population of some developed countries suffer some form of delusion-like psychological illness. Whether chronic somatic disease causes chronic psychological disease or the treatment of chronic somatic disease causes chronic psychological disease is still an open question.
SourceSaha S, Scott J, Varghese D, McGrath J. The Association between Physical Health and Delusional-Like Experiences: A General Population Study. PLoS One. 2011 Apr 25;6(4):e18566.: