Introduction: This study aims to assess the prevalence rates of mental disorders and chronic medical conditions in the Singapore resident population, and examine their association and respective impact on the quality of life.Materials and Methods: A household survey was carried out on a nationally representative sample of the adult (18 years and above) resident population. The main instrument used to establish the diagnosis of mental disorders is the World Mental Health Composite International Diagnostic Interview (WMH-CIDI). The mental disorders included in study were major depressive disorder, bipolar disorder, generalised anxiety disorder, obsessive compulsive disorder, alcohol abuse and alcohol dependence. Respondents were asked if they had any of the chronic medical conditions from a list of 15 conditions. Health-related quality of life was assessed with the EQ-5D. Results: Of the 6616 respondents, the lifetime prevalence of mental disorders was 12.0%, and that of chronic medical disorders were 42.6% and those with comorbid mental and medical disorders was 6.1%. The prevalence of any physical disorder in this population was high (42.6%). Among those with chronic physical disorders, 14.3% also had a mental disorder, and among those with mental disorders, more than half (50.6%) had a medical disorder. Most of the mental disorders were not treated. Males, Indians, older people, and those who were separated or divorced were more likely to have comorbidity. The health-related quality of life was significant worse in those with both mental and medical disorders compared to those with either mental or medical disorder. Conclusion: Our study re-emphasised the common occurrence of mental and medical disorders and the importance for an integrated care system with the capability to screen and treat both types of disorders. It also identified certain subpopulations which are more likely to have comorbidity for which a more targeted intervention could be planned.
The co-occurrence of mental and medical disorders in the same person, regardless of the chronological order in which they occurred or their causal relationship—commonly referred to as comorbidity—is not uncommon. The National Comorbidity Survey Replication (NCS-R), which was a nationally representative epidemiological survey in the US, found that at least 68% of adults with a mental disorder had at least one general medical disorder, while 29% of those with a medical disorder had a comorbid mental health disorder. Research across a swathe of countries has consistently shown that people with mental illnesses have high rates of physical illnesses that were largely not diagnosed.
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