Psychiatric Symptoms Disorders, Epidemiology, and the Risk for Diabetes

Diabetes mellitus (DM) is an increasingly prevalent and complex chronic illness with significant psychosocial and psychiatric ramifications. Stress and psychiatric illness can contribute to the development of the disease itself, via neurohormonal pathways and the side effects of psychiatric medication treatment, and psychiatric symptoms and disorders are prevalent and can have profound effects on the disease course of diabetes.

Thus, there is a pressing need for integration of general medical care and psychiatric care for the diabetic patient in order to improve quality of life and illness outcomes. This chapter will provide a background to appreciate the interplay between mental health and diabetes by distilling the current literature. We review the epidemiology of psychiatric disorders in diabetes, the effects of psychiatric symptoms and disorders on the course of diabetes, psychiatric and neurocognitive comorbidities caused by diabetes, and psychiatric treatment of the diabetic patient. With this summary, we hope to offer the clinician an appreciation for how to recognize and treat psychiatric aspects of diabetes and when a referral for psychiatric or other mental health consultation is likely warranted.

Psychiatric Symptoms and Disorders and the Risk for Diabetes

There is now abundant literature to suggest that psychiatric symptoms and disorders often precede the onset of diabetes and may in fact comprise independent risk factors. Large epidemiological studies have documented that the presence of depressive and anxiety symptoms at a baseline measurement predicts the later onset of metabolic syndrome and diabetes. In a prospective population-based Norwegian study, Engum found that individuals reporting symptoms of depression and anxiety at baseline had increased risk for onset of type 2 diabetes at 10-year follow-up, after controlling for established diabetes risk factors. Interestingly, baseline diabetes was not associated with the presence of depressive or anxiety symptoms at follow-up (see next section).

In a Swedish cohort of approximately 5200 individuals followed for 8–10 years, Eriksson et al.1 found that the presence of distress symptoms at baseline (anxiety, apathy, depression, fatigue, and insomnia) predicted the onset of abnormal glucose tolerance and diabetes for men and abnormal glucose tolerance for women. The potential etiological mechanisms mediating the relationships between depression/anxiety/distress and diabetes are speculative, complex, and involve both neurohormonal and behavioral mechanisms. Depression/anxiety and prolonged stress affect the entire neuroendocrine system via activation of the central sympathetic nervous system and hypothalamus–pituitary–adrenal (HPA) axis. Activation of the HPA axis causes excessive cortisol production that induces insulin resistance, dyslipidemia, visceral obesity, and type 2 diabetes. Also, depression may diminish healthy dietary and physical activity, leading to cardiovascular and diabetes risk.

In addition to depression and anxiety, there is now a growing literature linking other forms of mental illness including schizophrenia, schizoaffective disorder, and bipolar disorder to the risk for diabetes. This relationship has been found to exist independently of the known effects of antipsychotic medications (particularly the second-generation atypical antipsychotics) on weight gain and glucose homeostasis (see below). Patients with schizophrenia, independent of antipsychotic medication use, are two to three times more likely than the general population to have type 2 diabetes. In one hospital-based sample, 50% of bipolar and 26% of schizoaffective disorder patients were found to have type 2 diabetes. In addition to the disorders themselves, newer generation atypical antipsychotic medications, particularly clozapine and olanzapine (and to a lesser degree and more inconsistently, risperidone, quetiapine, ziprasidone, aripiprazole) have been associated with dyslipidemia, insulin resistance, and hyperglycemia.

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