The Significance of the Heart-Brain Connection

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Why do we have so many expressions related to the heart? "To pour one's heart out," "A change of heart," "It's with a heavy heart." You can probably think of many more. Collectively, these expressions assume that the heart is not only a machine that pumps blood but also the seat of emotions (aching heart, broken heart), reason, and personality (bleeding heart, faint heart). Nobody says, “Follow your liver.” Only a comedian would say, “The pancreas has its reasons of which reason knows nothing.”

While these expressions and metaphors about the heart reflect centuries of folk wisdom, it seems that the ideas we acquaint in our collective unconscious with the heart as a center of thought, feeling, and personality are closer to recent discoveries in neurocardiology than scientists have previously assumed.

Not Just a Pump

The heart contains an intrinsic nervous system that exhibits both short and long-term memory functions. The intrinsic nervous system of the heart consists of approximately 40,000 neurons called sensory neurites which relay information to the brain. It is possible that these neurons play a pivotal part in memory transfer.

What is truly surprising is the discovery that the heart also functions as an endocrine organ. In other words, like the thyroid gland or the adrenal gland, it produces several hormones, including the cardiac natriuretic peptide. This hormone exerts its effect on the blood vessels, the kidneys, the adrenal glands, and on a large number of regulatory regions in the brain.

It was also found that the heart contains cells known as "intrinsic cardiac adrenergic" cells, which release noradrenaline and dopamine.

More recently, it was determined that the heart also secretes oxytocin, commonly known as the love or bonding hormone. Concentrations of oxytocin in the heart were found to be as high as those in the brain.

The Heart and Mental Disorders

A recent study from Denmark takes us in a different direction. The study involved 10,632 adults born between 1890 and 1982. Using medical registries and medical records from all Danish hospitals, the researchers identified adults who were diagnosed between 1963 and 2012 with congenital heart disease. These individuals had a 60 percent higher rate of dementia compared to the general population. The risk was 160 percent higher in people younger than 65. Why would that be?

Previous studies have linked negative emotions, including depression, anxiety, and anger, to a heightened risk of heart disease. Because these emotions tend to overlap and coexist, it's been difficult to assign a relative importance to any one of them.

When it comes to myocardial infarction, the medical term for a heart attack, evidence is accumulating that if a person develops a major depression following a heart attack, a rather common occurrence, they will be consistently at a three-fold increased risk of death.

According to new research from Rice University and Northwestern University, people who recently lost a spouse are more likely to have sleep disturbances that make them more vulnerable to develop inflammation, which in turn raises their risk to develop cardiovascular illness and death.

These are examples of the perfectly designed ecosystem our body represents. The moment one of its elements changes, everything else is affected, and hardly ever in a good way.

Moving from depression to schizophrenia, the leading cause of death among people suffering from schizophrenia is coronary artery disease. The average life expectancy of the general population in the U.S. is 76 years (72 years in men, 80 years in women), compared to 61 years (57 years in men, 65 years in women) among patients with schizophrenia. Thus, individuals with schizophrenia have approximately a 20 percent reduced life expectancy relative to the general population.

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Cardiologists believe that factors such as antipsychotic medications, cigarette smoking, obesity, diabetes, and hypertension are responsible for escalating morbidity and mortality in schizophrenic patients.

Sustained stress, anger, and anxiety can disrupt cardiac function by changing the heart’s electrical system, hastening atherosclerosis, and increasing systemic inflammation. “But negative emotions are only one-half of the equation,” says Laura Kubzansky, Harvard School of Public Health. “It looks like there is a benefit of positive mental health that goes beyond the fact that you’re not depressed.”
In a 2007 study, Kubzansky followed more than 6,000 men and women aged 25 to 74 for 20 years. The protective effect of emotional vitality was distinct and measurable, even when taking into account such wholesome behaviors as not smoking and regular exercise. Kubzansky has found that optimism cuts the risk of coronary heart disease by half.

Conclusion

Research in the relatively new discipline of neurocardiology has confirmed that the heart acts as a sophisticated information encoding and processing center that enables it to learn, remember, and make functional decisions independently of the cerebral cortex. Additionally, numerous studies have demonstrated that cardiac signals to the brain affect autonomic regulatory centers and higher brain centers involved in cognition and mood regulation.