Diabetes and Schizophrenia: Causes and Research for Cures

My interest in the link between diabetes and schizophrenia comes from having had a friend who has both. He was seventeen when diagnosed with juvenile diabetes. The schizophrenia came along five to ten years later.

These dual health developments condemned him to a life of daily blood sugar testing, insulin injections, and food monitoring. He also takes Risperdal for the schizophrenia.

We wondered if there was a connection between schizophrenia and diabetes. His intuition told him there was, and a research article published in PLoS Biology in June 2010 confirms this link.

In a June 9, 2010 article in Science Daily, Kevin Niswender, M.D., Ph.D, an endocrinologist who worked on the PLoS Biology research article, was quoted as saying, "We know that people with diabetes have an increased incidence of mood and other psychiatric disorders."

[Reference links to the Science Daily article and PLoS Biology's research article are included near the bottom of this page.]

The body's glucose metabolism is regulated by the hormone, insulin, which is normally secreted by a healthy pancreas whenever glucose or protein are detected in the blood, after a meal.

A person with type 1 diabetes mellitus (Juvenile Diabetes) develops insulin deficiency (autoimmine-mediated destruction of insulin).

Type 2 diabetics develop insulin resistance associated with genetics, obesity, lack of exercise, and age.

Insulin also regulate more than just glucose - it regulates dopamine as well. Lack of dopamine, a neurotransmitter, is associated with schizophrenia and other maladies such as Parkinson's disease, ADHD, social withdrawal, and depression.

The PLoS Biology article's research team's discovery is that insulin deficiency or resistance change neurotransmitter levels in the brain. They found reduced dopamine and increased norepinephrine in the prefrontal cortex. A transporter protein called NET is responsible for altered neurotransmitter levels.

In the June 9, 2010 article in Science Daily, Aurelio Galli, Ph.D, a neurobiologist who participated in the research project, is quoted as saying: "We believe the excess NET is sucking away all of the dopamine and converting it to norepinephrine, creating this situation of hypodopaminergia (low levels of dopamine) in the cortex."

Not all people with diabetes develop schizophrenia. This study simply confirms that many schizophrenics had diabetes and insulin deficiency as a contributing factor to their mental illness.

The study also suggests a new treatment for schizophrenia that is now in the testing phase.

The PLoS Biology research article's author summary states, "...dysfunction of dopamine signaling in the brain is one of the final common pathways involved." This refers to the final stages leading to schizophrenia.

This suggests that well-controlled diabetes is less likely to cause schizophrenia than diabetes that is not controlled with medical intervention.

My friend with the diabetes and schizophrenia was only seventeen when his diabetes was diagnosed. Prior to that he'd spent five years in foster homes or as a teenaged street person. When he didn't like a foster home, he'd run away. He was on the streets for years . . . until he collapsed and was diagnosed with juvenile diabetes.

After his diagnosis he continued a life that was irresponsible at best. He had no contact with his parents - his mother was in a mental hospital with bipolar disorder - something he has never developed. His father had offered him a home but that didn't last for more than a year before a severe rift developed.

My friend continued to drift until he became a cult member and decided that God would save him from diabetes. He decided to discontinue his insulin and trust in the Lord. This nearly killed him and he ended up back in a hospital being treated for diabetes.

Perhaps his lifestyle contributed to the development of schizophrenia after his diabetes diagnosis. Of course, I can't say for sure - and probably nobody can - but I believe his family situation and choices contributed to his development of schizophrenia.

I didn't meet him until he was 37 and by then he'd settled into a responsible pattern of caring for his diabetes correctly most of the time, despite his schizophrenia. Also while I was living with him, he started taking Risperdal and was able to control some schizophrenia symptoms that had caused a variety of problems for him over the years.