Psychiatric aspects of diabetes
This page provides an overview of this section of Diapedia which covers the relationship between diabetes and mental illness, in particular focussing on the association with depression, severe mental illness (schizophrenia and bipolar illness) and eating disorders. Within each of the sections, there are pages on the epidemiology of the co-morbidity, mechanisms underlying the association and clinical implications.
The greatest challenge facing medicine in the 21st century is multimorbidity, the co-occurrence of two or more diseases together in the same individual . Multimorbidity is becoming increasingly common; by the age of 55 years, two thirds of people with a chronic disorder have more than one illness at the same time. Diabetes specialists are used to managing this challenge and have a good understanding of how diabetes can impact on other specialties, such as ophthalmology or renal medicine. However, the co-morbidity of diabetes and mental illness is less well appreciated despite it being common and having adverse effects for diabetes and mental illness outcomes . Psychiatric illness hinders the ability of the individual to undertake diabetes self-management which is central to the maintenance of health and prevention of complications and premature mortality. Therefore an understanding of the complex interaction between mind and body is crucial to the management and outcome of people with diabetes.
Mental illness is remarkably common in the population and so some co-morbidity in people with diabetes may occur purely through chance. Research over recent decades has shown, however, that many mental health problems occur more frequently than expected in people with diabetes while people with mood and psychotic disorders are at significantly increased risk of developing diabetes.
The prevalence is depression and depressive symptoms is approximately two-fold higher in people with diabetes compared with the general population . The co-occurrence of depression not only impairs quality of life but also leads to poorer diabetes self-care which in turn may explain the higher rates of diabetes complications and premature mortality seen in those with depression. Depression outcomes also appear to be worsened in those with diabetes.
Depression is commoner in people with a range of chronic illnesses, including cardiovascular disease and cancer, and common pathways to explain this increase may occur. Diabetes places a significant burden on the affected individual, both in terms of knowledge of the illness and consequences and its treatment. While this psychological burden of diabetes may contribute to depression, other mechanisms may also be important including hypothalamic-pituitary-adrenal axis dysfunction, inflammation, sleep disturbance, and environmental and cultural risk factors. Furthermore both hyper- and hypoglycaemia may adversely affect brain function in areas responsible for mood .
Despite effective screening tools and well validated treatments, depression is frequently missed in people with diabetes. Some of this may reflect the person with diabetes who may ignore the depression or regard their low mood as “understandable” in the context of diabetes. There is also on-going fear of stigma and medication side effects. On the other hand, healthcare professionals may overlook depression in someone with a physical health problem and misdiagnose it as a somatic complaint.
Once a diagnosis is made, effective treatment pathways are needed. Both psychological interventions and antidepressants will alleviate depressive symptoms in people with diabetes although there are mixed effects on glycaemic control, with general better effects with psychological treatments as these often combine diabetes education .
Severe mental illness
The prevalence of type 2 diabetes is approximately 2-3 fold higher in people with severe mental illness (schizophrenia and bipolar disorder). Epidemiological studies have demonstrated that between 10-15% of have diabetes and suggest that the onset is around a decade earlier than in the general population . Furthermore up to 70% of cases of diabetes are undiagnosed in people with severe mental illness.
The consequences of diabetes for people with severe mental illness are worse as they are more likely to develop acute metabolic complications, are more likely to develop chronic microvascular and macrovascular complications and more than six-fold more likely to die from diabetes.
The mechanisms underlying the association between diabetes and severe mental illness are multifactorial and include genetic and lifestyle (poor diet, physical inactivity and smoking) as well as biological (similar to depression) and treatment factors.
Many national and international guidelines recommend that people with severe mental illness should undergo screening by blood testing (glucose or glycated haemoglobin (HbA1c) prior to the onset of treatment, 2-3 months later to assess any acute change in glucose in response to treatment and thereafter on an annual basis .
It is important to consider ways to prevent diabetes in people with severe mental illness. Although formal diabetes prevention trials have not been undertaken in this patient group, lifestyle interventions are possible in people with severe mental illness, with people with schizophrenia reported to achieve significant weight loss with on-going support .
The additional challenges of managing co-morbid diabetes and mental illness require close collaboration between mental and physical health services, but the treatment of diabetes in people with severe mental illness should largely follow existing treatment algorithms for the general population.
There are currently four eating disorders commonly diagnosed in adults, anorexia nervosa, bulimia nervosa, binge eating disorder and eating disorder not otherwise specified. Individuals with type 1 diabetes (T1DM) seem at particular risk of developing an eating disorder, in whom the combination can lead to significant morbidity and mortality . This increase may occur because of the non-specific stress of having a physical illness although dietary restriction and insulin therapy may be specific risk factors. Individuals with T1DM may experience body dissatisfaction and a stronger desire to lose weight because they are likely to be heavier than those without diabetes. Furthermore people learn rapidly that the under-use or omission of insulin can be used to manipulate weight. Clinicians need to be aware of the possibility of an eating disorder and diabetes teams will need to work closely with the mental health team to achieve optimal treatment.
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