Diabetes and the Brain

It’s hard enough managing diabetes when you have all your mental faculties, right? Well, for a lot of people, it’s worse. They have diabetes and mental illness, too.


Web editor Tara Dairman put me on to this story after a reader asked about it, and it turned out to be interesting enough to share.

Are mental illness and diabetes linked?
According to The New York Times, “among the mentally ill, roughly one in every five people appear to develop diabetes—about double the rate of the general population.”

The reverse also appears to be true. Research has found that as many as one in five children with newly diagnosed Type 2 diabetes (now there’s a depressing phrase) may also have a neuropsychiatric disorder.

The illnesses include depression, attention deficit hyperactivity disorder (ADHD), autism, developmental delay, schizophrenia, and bipolar disorder. The research suggests that children with a neuropsychiatric disease may be at risk for Type 2 diabetes, and vice versa. At the other end of life, Alzheimer disease has also been linked with diabetes and other insulin problems. But why?

What’s the connection?
Some people blame the meds that people with serious mental illness receive. They tend to cause major weight gain which could trigger Type 2 diabetes. Others say that depression contributes to diabetes by making people sedentary. But that doesn’t explain the bipolar disorder, schizophrenia, Alzheimer disease, and the others. It may well be that insulin plays a major role in brain function. When insulin processing is damaged, psychiatric problems can result.

An article by science writer Scott Allen reports on recent research showing that Alzheimer disease and schizophrenia, two of the most challenging mental illnesses, “could be secondary to a breakdown in the way brain cells process insulin.” Researchers are throwing around terms like “Type 3 diabetes” and “diabetes of the brain” to describe these conditions.

Whether an insulin shortage “causes [schizophrenia], contributes to the disease, or it’s the brain’s response to injury, we don’t know yet,” said Jesse Roth, M.D., F.A.C.P., geriatrician-in-chief of the North Shore–Long Island Jewish Health System in New York, who has studied insulin’s role in the brain since the 1980’s.

According to Allen, “Dr. C. Ronald Kahn, president of the Joslin Diabetes Center in Massachusetts…suggests that insulin problems in the brain may, in turn, make people more vulnerable to Type 2 diabetes.” Lab mice modified to block insulin processing in the brain became obese and showed signs of diabetic insulin resistance.

Insulin as brain therapy
For a while, doctors were treating schizophrenia by putting people into insulin shock. Some, such as John Nash, Jr., the mathematician portrayed in the movie “A Beautiful Mind,” actually benefited, but up to 10% of the patients died, and by the early 1960’s the treatment had been stopped.

In 2005, researchers at Psychiatric Genomics discovered that the same 14 genes that are missing in the brains of people with schizophrenia are also missing in muscle tissue of people with diabetes. In the lab, they were able to increase the availability of those genes by giving insulin, which could lead to new therapies for schizophrenia.

Other scientists are studying whether inhaled insulin improves memory in people with Alzheimer disease.

I don’t know that any of this information helps people deal with diabetes. But it does give a glimpse into how incredibly complicated our bodies are, and how important insulin function is, and how our brains and bodies might be connected. And the probable association between Type 2 and later mental illness gives us another reason to help children and families avoid diabetes in the first place.

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  • CalgaryDiabetic

    Dear David. Another super bad news correlation. It is not surprising that there may be more to the problem than the obvious: The more you are depressed (or the more dead tired you are from diabetes) the less you will exercise and the worst both diabetes and depression will become. This in engineering is called positive (not positive in the psychological sense but because you add i.e. + to a bad state instead subtracting i.e. – from the bad state) feedback which is unstable. The NY Times article raises the possibility (one would think near certitude) that many vital organs in diabetics lack the ability to transport glucose to their cells to function effectively. Not only the brain but how about the hypothalmus and God only knows what else. When years ago my GP asked me how I felt when everything on paper was at its best. I said I run as a well tuned American V-8 with 2 spark plugs removed. And of course when the BG is out control you feel even worst. Under these conditions it is difficult not to get depressed and onwards vicious circle. There are some mental techniques somewhat useful to deal with this if you find some blog them.

  • YumaMamaLama

    Hi, David

    I read your article with great interest, because I’m of an age where I become “eligible” for the Type 2 DM/Alzheimer’s connection concerns.

    One thing that you wrote, though, I feel needs to be expanded upon.

    While it’s true that many of the medications used for both bipolar disorder and schizophrenia can cause weight gain, the medications do differ in their propensity to do this. I don’t mean that anyone should dismiss the apparent connections between obesity and Type 2 DM, however it is not just a weight gain problem from using these medications that can lead to DM. These medications also can cause metabolic changes, including insulin resistance and DKA. 25% of those who develop Type 2 DM after using these meds have not gained weight from them.

    In 2003 the FDA issued a statement to the makers of all atypical antipsychotics that they needed to change their warning labels to state specifically that there is a link between the meds and hyperglycemia — which may or may not lead to diabetes. With some of the medications, hyperglycemia is reversible — that is, stop taking the meds, and the hperglycemia fades away.

    Psyciatric News from October 17, 2003 (Volume 38, Number 20) has relatively general articles on this problem on pages 1 and 26. [ Url’s are: http://pn.psychiatryonline.org/cgi/content/full/38/20/1-a and http://pn.psychiatryonline.org/cgi/content/full/psychnews;38/20/26 ]

    There are also papers/articles on PubMed that discuss the metabolic effects of these medications.

    A change of topic: Will you be having some info regarding the skeletal system’s affect on blood sugar regulation?

    I’ve been a reader of both the hardcopy and online issues of Diabetes Self Management for some time, and always enjoy your articles.

  • David Spero RN

    Dear Mama,
    Thanks for the good info on antipsychotic drugs. I don’t know what you meant by skeletal system’s effects. Tell us more.

  • Linda Mills Fouts

    This is one of the best blogs I have read of late. It particularily peaks my interest as I am one of those who has comorbid bipolar disorder and Type II diabetes. The references are great, as well as some of the reader comments. I hope research continues in this area and that perceptive writers like yourself continue to “spread the word” — Thanks!

  • Michael.Massing

    This is an overdue conversation. When I was diagnosed at the end of 2002 (at least four years after clearly manifesting symptoms), there was hardly any information available about mood and cognitive correlations with – and I would say effects of – diabetes. Why do I say “effects”? In brief, because as a chronic (manageable) depressive with an IQ of about 140, I found the period immediately before type 2 diagnosis to be marked by escalating blood sugars, weight spiraling out of control, and mental slowness and stupidity such as I have not experienced before or since. With aggressive management via diet and exercise, I brought my blood sugar levels back into the normal range and – guess what? – regained my former mental acuity. We have much to learn in this area and should, indeed must, be looking closely at our experiences, recording them accurately, and reporting them to our health care professionals.

  • CalgaryDiabetic

    Dear David. It is also hard to find the effects of diabetes on sleep or even sleep on diabetes. You would think that being a chronic disease you would sleep like a rock which was the opinion of my first diabetic specialist. No so, slightly high blood sugar and I find it difficult to fall asleep and too low you wake up in a panic. Ideally BG in the 70 to 80 range is great for falling asleep as long as it does not fall lower which is easy to say but not easy to do. I find staying asleep more than 4 hours impossible regardless of the blood sugar readings. Again I had to urinate again even if BG is in the normal range. Any thoughts?

  • basketcaz

    I was diagnosed with type II diabetes four years ago. Up to two years before that I noticed a rise in my levels of depression, anxiety and an inability to deal with noise. My cognitive skills had declined to the point that I could barely talk…forgetting a word and then what I was even talking about. And yes, insomnia. Since I started on insulin (last October) my mind has come back; YEAH. I was hoping that my mental health and sleep problems would get better too; but no.

    This blog was very interesting along with the responses. I hope that this subject will be expanded upon. Thank you.

  • spedhead

    This is interesting and gives credence to suspicions I have had for several years in regard to my teenage daughter-she was diagnosed with Bipolar disorder at 16-been on heavy duty meds ever since and struggled with weight gain. The past 6 months her depression deepened to point of hospitalization and ECT–and all the while every blood test showed high BG levels and A1C of 12 or higher–I questioned re. diabetes–was told it was result of meds and weight gain. She was JUST diagnosed as diabetic-placed on insulin–and lo and behold, is feeling better by the day! Combination of ECT and insulin–whatever it takes to keep her alive! Anyway–great info. from all involved-

  • Jennifer

    I am a 28 yr old female with Type 2 diabetes, anxiety, panic, agoraphobia and depression. I have noticed that when my sugar levels are at certain levels especially 180+ I get very aggitated and have alot of negative anxious thoughts. I have been reading alot lately on this to see if they are linked. What do you think?

  • David Spero RN

    Hi Jen,

    As you can see from the comments here, a lot of people find that glucose control makes a big difference in thoughts and feelings. I would say try to keep the glucose closer to normal and see what happens.

    I had forgotten all these great letters from last year. I’ll write about this again soon.


  • f, Marc Sabatini

    any info on how the brain reacts with long term type 1, say 54 years, blood glucose back and forth, up and down all your life?