Of all the organs inside the human body, the brain uses by far the most energy. In order to allow us to breathe, think, feel, and stay alive, the brain requires a steady supply of glucose. Given this, it should come as no surprise that abnormal blood glucose levels could impact cognition and emotional stability.
Our understanding of the connection between blood sugar and mental health is only just becoming clear. But already, researchers have identified continuous blood glucose monitors (CGM) as a helpful tool for treating everything from anxiety to schizophrenia.
In this article, we examine the link between blood glucose abnormalities and mental health problems and how CGMs might be useful in both the medical and commercial fields for helping people take control of their mental health.
The Connection Between Blood Glucose and Cognition
In addition to being one of the most glucose-hungry organs in the body, the brain is also one of the few that doesn’t require insulin to utilize glucose. That means that shifting blood glucose levels have a more dramatic impact on brain cells than they do on other organs and bodily systems.
High and low blood sugar levels, as well as swings in blood sugar, all impact how the brain functions. These effects can be relatively short-lived or long-lasting, depending on the severity of the damage.
Hyperglycemia
Hyperglycemia, or high blood glucose, can cause a host of emotional and cognitive problems, including:
- Irritability
- Mood swings
- Depression
- Anxiety
- Impaired concentration
- Addictive cravings
High blood glucose and blood glucose abnormalities have also been linked to schizophrenia. One study looking at newly diagnosed, drug-naive schizophrenic patients found that the dopamine-glucose relationship in these people was altered compared to healthy controls. In non-schizophrenics, low blood sugar is associated with high extracellular dopamine levels, and high blood sugar is associated with low dopamine. In schizophrenics, this relationship is reversed(1). The brain uses dopamine to stimulate energy-seeking behavior. When dopamine is released in response to high blood sugar, it creates a cycle of overeating that leads to extended periods of hyperglycemia.
It is well established that schizophrenics have a five times greater risk of developing type 2 diabetes than the general population. This association has long been attributed to unhealthy lifestyles and the effects of antipsychotic drugs. But studies like the one mentioned above seem to indicate that the relationship between the two exists before the first symptoms of schizophrenia present themselves. Furthermore, it is possible that damage to the brain caused by chronic hyperglycemia may influence the progression of the disease.
Hypoglycemia
Hypoglycemia, or low blood sugar, causes a range of acute problems that can become chronic when glucose levels remain impaired for extended periods. These problems include:
- Anxiousness
- Panic attacks
- Depression or thoughts of self-harm
- Mood swings
- Irritability
- Impaired concentration
- Sleepiness
- Memory disruption
Observational studies, including one that followed a young woman with generalized anxiety disorder and hypoglycemia symptoms, indicate a clear link between certain mental health issues and chronic hypoglycemia. In this case, a diet made up largely of refined carbohydrates caused frequent hypoglycemia for the patient in question. After her diet was modified to include fats, protein, and complex carbohydrates, her anxiety symptoms went away(2).
Hypoglycemia also has the potential to cause long-term damage. When blood sugar levels plummet too low or are maintained at low levels for too long, some areas of the brain are deprived of nutrients. Without energy to function, cell death occurs. It is possible that repeated hypoglycemia could lead to irreparable damage to certain areas of the brain.
Blood Sugar Swings
Chronic high or low blood sugars aren’t the only blood glucose problem that affects the brain. Wide swings in blood sugar can also cause mental and emotional symptoms, even when average blood glucose levels remain within a normal range.
Symptoms of frequent blood glucose swings include:
- Poor fact recall
- Poor memory
- Impaired cognition
- Reduced mental alertness
The side effects of volatile blood glucose have been well-established in the diabetic community. But more recent studies have found that the same negative effects on cognition caused by fluctuating blood glucose can be seen in healthy individuals with normal fasting glucose levels.
One study looked at young, nondiabetic adults with normal fasting blood glucose levels. The participants were given glucose tolerance tests to measure blood sugar rise after ingestion of a high glycemic index drink. Separate from these tests, each participant was also given a set of cognitive tests. The researchers found that those who scored the worst on the glucose tolerance test also had the worst scores on the cognitive tests(3). This was true despite similarities in insulin levels and fasting blood glucose levels across all participants.
We know that frequent changes in blood glucose cause oxidative damage to the cardiovascular system. It’s possible that this damage leads to damage within the brain due to decreased blood flow. It’s also possible that this same oxidative damage or something similar occurs within the brain during periods of extreme blood glucose flux.
Blood Glucose and Common Mental Health Problems
Blood glucose levels are clearly connected to mental health and common emotional and cognitive disturbances. And yet, few doctors or patients consider blood sugar when prescribing treatment. Using CGMs to monitor patients undergoing mental health treatment could provide valuable insight into alternative treatment options, effective lifestyle changes, and the relationship between diet and mental health. How these devices would be most effectively used depends on the condition in question.
Anxiety
Anxiety is a common symptom in both hypoglycemia and hyperglycemia. Patients suffering from occasional or chronic low blood sugar are likely to feel sudden, acute anxiety with no apparent cause. In cases of extremely low blood sugar or fast drops in blood sugar, these anxious feelings may progress into panic attacks. Hyperglycemia is more likely to produce chronic anxiety marked by obsessive thoughts and feeling overwhelmed.
Pairing a CGM with a smartphone application that allows users to self-report symptoms could quickly identify associations between blood glucose levels and feelings of anxiety. Adding a connected vitals monitor that tracked pulse, blood pressure, and perspiration could remove the need for user input completely.
Irritability and Mood Swings
Mood swings are common with changes in blood sugar, especially when sugars fall or increase rapidly. Extended hyperglycemia brings feelings of fatigue and mental fog that often lead to irritable outbursts. Hypoglycemia can change a person’s energy levels quickly, leading to an unstable mood and emotional outbursts.
Pairing a CGM with a user-friendly app that includes prompts to record mood throughout the day could help identify glucose levels that drive irritability and if mood swings are associated with swings in blood sugar or consistently high or low glucose trends.
Depression
Depression is a common symptom in those who suffer from chronic hyperglycemia. Reduced energy levels, confusion associated with cognitive decline, and anxiety are all symptoms of hyperglycemia and contribute to feelings of depression. It’s also likely that sustained hyperglycemia causes changes in hormones released by the brain. Hypoglycemia can also cause sudden and inexplicable feelings of depression that are usually relieved once blood sugar levels are brought back to normal.
As with anxiety, a combination of wearable vitals monitors, a CGM, and an app that allows users to record symptoms could go a long way in identifying a connection between blood glucose and depressive feelings.
Schizophrenia
Hyperglycemia appears to be an early symptom of schizophrenia and may prove valuable in identifying at-risk patients before their first schizophrenic episode. A CGM would be especially effective if paired with a wearable that could track dopamine levels in order to identify abnormal interactions between the two.
In those already diagnosed with schizophrenia, a CGM could help alert care teams to changes in blood sugar caused by worsening metabolic health or medications.
Memory and Cognition
Swings in blood glucose can cause damage resulting in impaired memory and reduced cognitive ability. Unfortunately, by the time many people realize they are in cognitive decline, it is already too late.
There are already a number of apps on the market that use CGMs to help people take control of their physical health. These could be easily expanded to encompass the effects of blood sugar on cognition using memory tests and other simple measures of mental aptitude.
Opportunities for CGM Use in the Mental Health Market
The first step to using continuous glucose monitors to help people take control of their mental health is to identify if a connection exists between their blood glucose levels and their symptoms. The second step is to utilize this information to establish a treatment path for the patient, the care team, or both. Depending on the ailment in question, these applications could be developed and marketed to the medical community or directly to consumers.
As with many CGM apps utilized by the diabetic community, CGM software used for mental health could easily connect to doctor-facing platforms. These would allow care teams real-time access to their patient’s data in order to make changes to medications or recommend lifestyle and diet modifications.
In the commercial realm, the possible uses for this kind of tech are boundless. We’ve already seen diet and weight management apps utilize CGMs to give their users greater insight into how their body reacts to different kinds of food and exercise. This same concept could be used to help those with mental health issues identify problematic foods and activities that contribute to blood sugar abnormalities that make their symptoms worse.