Investigating the link between Type II diabetes and mental illness

Serious mental illness affects the mind and the body. After all, the mind and body are connected.

In fact, previous research show that patients with major mental illness die 15 to 30 years earlier than the average. But most of the excess mortality stems from medical causes unrelated to the brain or nervous system. For example, the original major tranquilizers and anti-psychotic drugs adversely affected the brain, creating tremors and Parkinson’s disease symptoms in patients.

(Interestingly, nicotine is a very effective treatment for Parkinson’s symptoms. In fact, in earlier years, psychiatric patients — typically disabled by the illness and their medications — learned they could reduce these drug-induced side effects by smoking. They also had nothing else to occupy their time, so they would smoke up to four packs per day — well beyond the amount from which the lungs can protect themselves. They suffered increased rates of lung cancer and other lung diseases.)

Type II diabetes is another example of a non-brain-related condition associated with mental illness. In fact, experts estimate that Type II diabetes rates run up to three times higher in patients with major mental illness. However, it has always been unclear what caused in the increase in risk.

But a new study out of King’s College in London investigates the connection between mental illness and Type II diabetes.

What comes first — mental illness or impaired blood sugar metabolism?

Researchers from Kings College tried to untangle the causes in the new study. Is the increased risk due to underlying causes of the mental illness? Is it caused by the mental illness itself? Or is Type II diabetes a side effect of treatments for mental illness?

Researchers reviewed 16 case-control studies to determine whether blood sugar metabolism was impaired in patients with their first episode of major mental illness.

The total sample included 731 patients and 614 healthy controls. And the researchers matched the mentally ill patients against healthy controls for body mass index (BMI), diet, and exercise levels.

Patients with mental illness in the study were otherwise physically healthy. And they had no illnesses that would be expected to adversely affect blood sugar metabolism. In addition, they had not received any psychiatric medications previously.

Overall, the researchers found that patients with mental illness had significantly higher blood sugar and insulin levels. They also showed signs of insulin resistance.

They did not, however, show any significant differences in hemoglobin A1C levels, the traditional measure of long-term blood sugar levels over a period of four to six months.

Of course, antipsychotic drugs themselves can cause Type II diabetes. But these patients were chosen because they hadn’t taken any antipsychotic drugs previously.  Poor diet and exercise are also risk factors for developing Type II diabetes. But the researchers controlled for these factors in their analysis as well.

In my view, this new research demonstrates that alterations in blood sugar metabolism are present from the very first onset of mental illness. The high rate of Type II diabetes in patients with new-onset major mental illness may also help explain the much higher mortality rates seen in these patients.

Of course, these dangerous metabolic symptoms can also cause other problems, in addition to Type II diabetes. For example, as you know, high blood sugar and insulin levels can also cause heart disease (far more important than cholesterol). Moreover, having Type II diabetes itself is a risk factor for developing heart disease.

Holistic approach needed for patients with mental illness

The researchers concluded that physicians need to take a more “holistic” approach to treatment of major mental illness. The mind and body are indeed connected, as I mentioned earlier. And it is not enough to dole out psychiatric medications by mental health professionals who have lost touch with the rest of the human body, if they ever had it.

This approach is even more critical because some psychiatric drugs worsen the risk of developing Type II diabetes in the first place. There is a reason psychiatrists have to go to medical school before receiving their prescription pads. And they should remember it when treating their patients.

As I have previously reported, other studies show physical activity, exposure to Nature and sunlight, and nutritional herbal supplements all help lower the risks of both mental and physical illnesses. And those experiences aren’t available on, or from, a prescription pad.


  1. “Impaired Glucose Homeostasis in First-Episode Schizophrenia,” JAMA Psychiatry ( 11/11/2017