Early Signs of Schizophrenia May Link to Diabetes

People experiencing early signs of schizophrenia are at risk for diabetes, and researchers are studying what the connection could mean for treatment.

Schizophrenia is a severe, chronic mental disorder that affects how a person behaves, thinks, and feels. It can include hallucinations and other disabling psychiatric symptoms, along with physical problems. For example, people with long-term schizophrenia have three times the risk of developing type 2 diabetes compared to those without the mental illness.

Type 2 diabetes, in turn, raises your risk of heart attacks and strokes — two of the main causes of death that reduce life expectancy in people with schizophrenia up to 30 years, according to researchers at King’s College in London, who are investigating how diabetes and schizophrenia are connected.

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It has been previously assumed that people with schizophrenia have an increased risk for developing type 2 diabetes because of poor eating habits, being sedentary, or antipsychotic drug side effects.

But a study by the King’s College researchers concludes that assumption is not the complete picture. They discovered a strong association between schizophrenia and diabetes exists when eating, sedentary, and medication factors are taken out of the equation. They also found that diabetes appears to develop early in the course of schizophrenia.

“These findings are a wake-up call that we need to rethink the link between diabetes and schizophrenia and start prevention right from the onset of schizophrenia,” said researcher Oliver Howes, MD, professor of molecular psychiatry at King’s College and senior author of the study. “It is a case of thinking mind and body right from the start.”

Howes and his team looked to see if people with early signs of schizophrenia had diabetes long before they were taking prescribed drugs and their symptoms resulted in unhealthy lifestyle habits. They analyzed blood tests from 16 studies of 731 patients diagnosed with a first episode of schizophrenia, comparing them with blood tests from 614 people in the general population.

The results showed the patients with early schizophrenia had significantly higher levels of fasting blood sugar than the healthy controls, indicating those with schizophrenia were at a higher risk for developing type 2 diabetes.

In addition, the people suffering with their first episode of schizophrenia had another sign of prediabetes. They had increased levels of insulin resistance, meaning their muscle, fat, and liver cells were not responding normally to insulin, a hormone the pancreas produces to help blood sugar enter cells.

The researchers saw the same results when they looked only at patients with early schizophrenia and controls who ate the same type of diet, exercised the same amount, and shared the same ethnicity.

That means lifestyle factors or ethnicity couldn’t explain the heightened risk for diabetes. Instead, it suggests something about schizophrenia likely plays a direct role in increasing the odds of developing type 2 diabetes.

The researchers also noted other factors — such as a premature or low birth weight — might raise the risk for both schizophrenia and type 2 diabetes. And, as schizophrenia symptoms start to develop, the stress hormone cortisol may rise, which could also play a role in diabetes.

“Our findings tell us that people with early schizophrenia have already started down the road to developing diabetes, even if they haven't been diagnosed with diabetes yet,” said Toby Pillinger, MD, a specialist in psychosis research at King’s College.

“Given that some antipsychotic drugs may increase the risk of diabetes further, clinicians have a responsibility to select an appropriate antipsychotic at an appropriate dose. Our results also suggest that patients should be given better education regarding diet and physical exercise, monitoring, and, where appropriate, early lifestyle changes and treatments to combat the risk of diabetes.”

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