For centuries, clinicians have been interested in the way diabetes and psychiatric symptoms interact with one another. Thomas Willis, in the 17th century, believed that diabetes was the result of “long sorrow and other depressions.” In the 19th century, Sir Henry Maudsley suggested, in his “The Pathology of Mind,” that “Diabetes is a disease which often shows itself in families in which insanity prevails.”
According to Yatan Pal Singh Balhara, the psychiatric symptoms and diabetes exist in a complicated interaction with one another. Diabetes certainly has psychiatric effects. Likewise, psychiatric disorders such as depression and schizophrenia are highly correlated with the subsequent onset of diabetes. It is also possible that hypoglycemic and ketoacidosis episodes are causally relevant to panic attacks the diabetic may experience. It is also well-known that problems with glucose tolerance and diabetes can result from medications used to treat psychiatric disorders.
Drugs used for recreational purposes, like tobacco and alcohol, can increase the possibility of developing diabetes by altering the pharmacookinetics of oral hypoglycemic substances. Smoking increases the risk of retinopathy, neuropathy, corony heart disease, stroke, peripheral vascular diseases and diabetic nephropathy.
Psychiatric problems can also contribute to the worsening of diabetes by influencing poor treatment adherence. Unfortunately, understanding the relation between diabetes and psychiatric disorders is complicated by low rates of detection. It is estimated that up to 45 percent of cases of psychiatric disorders go undetected in diabetic patients.
Hypoglycemic episodes of diabetes may themselves contribute to states of delirium. This is particularly true of diabetics who already suffer from psychiatric problems. This can manifest itself as either hypoactive or hyperactive delirium. In the latter, the patient moves around aimlessly and speaks in a way that does not make sense. In the case of hypoactive delirium, there is unusually low psychomotor activity. The individual may also hallucinate, exhibit thought disturbance, and struggle with sleep-wake cycle disturbances.
Co-occurrence of diabetes and depression is correlated with increased impairment and mortality. The risk of developing depression among diabetics is 50-100 percent higher than among the general population. Likewise, the prevalence of diabetes among those with bipolar affective disorders is higher than among the general population. This may be partially due to the side effects of psychotropic medications used for bipolar disorder. Diabetes is so highly correlated with depression because of biochemical changes such as hypercortisolemia, altered glucose transportation, leptin activity in the limbic system, and pro-inflammatory cytokines. Chronic use of antidepressants at moderate or higher doses nearly doubles one’s chance of developing diabetes. This is true of TCAs as well as SSRIs.
Those with schizophrenia are between 2-4x higher than the general population to develop diabetes. Family history of type 2 diabetes is likewise much higher among first-degree relatives of individuals with schizophrenia. The rate of impaired glucose tolerance in individuals with schizophrenia is around 40 percent. Antipsychotic medication, a sedentary lifestyle and poor healthcare all contribute to an increased risk of diabetes among those with schizophrenia.
Diabetes has likewise been found to cause structural and functional abnormalities in the brain. Scientists are thus concerned about the possibility that diabetes may contribute to the onset of dementia and cognitive dysfunction. Larger epidemiological studies make it clear that vascular dementia and Alzheimer’s disease are both more common among individuals with type 2 diabetes, even when controlling for variables such as hypertension, dyslipidemia and cardiovascular disease.
Habitual hyperglycemia may likewise contribute to cerebral dysfunction. There appears to be an inverse relationship to glycemic control and reasoning, learning and complex psychomotor performance. Another study correlated elevated A1C with reduced performance on neurocognitive tests assessing learning, memory and executive function. Patients with type 1 diabetes exhibit such cognitive deficits in mid-life. Neurocognitive changes such as lower motor speed and psychomotor efficiency are correlated with white matter volume reduction and microstructure alteration. Reduction in gray matter in parts of the brain responsible for memory and language processing has also been observed.