Low Blood Pressure and Depression

History of Research

The medical opinion on the connection between low blood pressure (hypotension) and major depressive disorder has vacillated over the years.  Prior to the 1940s, it was common for physicians to ascribe mental symptoms such as lassitude, fatigue, dizziness, sleep disturbances, anxiety and depression to a ‘constitutional hypotension’ or a ‘hypotensive syndrome.’

Studies at the time reporting symptoms of anxiety and depression to be associated with lower blood pressure measures fostered the general acceptance that low blood pressure was related to the syndrome. However, a series of reports highlighting the various health benefits of lower blood pressure measures and evidence that individuals with the highest levels of stamina and endurance actually maintained very low blood pressure, shifted the thinking of the field away from this belief.

More recently, this association has been reexamined with a fresh perspective.  Several studies conducted over the last decade have again reported a clear association between hypotension and symptoms of depression and anxiety, especially in the geriatric population.

Of special interest, a large Norwegian study of 65,648 men and women found a significant association of low blood pressure with anxiety and depression. The investigators reported an approximately 40% increase in the risk for anxiety or depression in individuals with systolic blood pressure measures in the lowest 5% of the population. Although there are several potential variables that may account for this finding such as the gender, age, use of specific antihypertensive medications, and the general health of the low blood pressure subjects, considering these variables in the analysis did not change the significance of the association in the study. Thus, there is again an increasing belief that some form of relationship exists between very low blood pressures and depressive symptoms.

It is important to be clear that the evidence of an association between low blood pressure and depressive symptoms does not mean hypotension is causing depression. The association only means that hypotension and depression are more commonly seen in the same individuals.  However, there is now interest in identifying what could be some of the common mechanisms underlying this relationship including difference in physical activity and stress reactivity, altered neuroendocrine, immune and/or autonomic regulation, and possible dysfunction of neurotransmitter systems and brain circuits regulating processes such as blood pressure and mood within the brain.

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Link between Low Blood Pressure and Depression

People with low blood pressure may suffer from depression owing to the large number of medications they are forced to take. But studies have also conducted that low blood pressure and depression might be because of some similar factors as well. This may be the case when there occurs a malfunctioning in the metabolism that are responsible for increasing or decreasing levels of metabolites. Changes in the hormones or neutron transmitters might be just some of the other factors which may be responsible for both low blood pressure and depression.

More importantly, low blood pressure is often accompanied with dizziness, tiredness and lethargy and thus the person who has low blood pressure may not feel well, become somewhat aloof from the rest of the world and thus may be depressed. Such people also find it difficult in holding their concentration at one place. There memory may also become loose. In a certain way, doctors also predict a two way relation between depression and low blood pressure. Since those who have low blood pressure are likely to become depressed and those who are depressed for a considerable longer period of time may develop low blood pressure.

On the other hand, high blood pressure has been linked to anxiety in the researches. This happens because of the stress level being experienced by the anxious people.

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Contradiction to Depression/Hypertension Theory

While the data related to the possible link between depression and low blood pressure, is not a new discovery, the results of the associated studies seem to contradict the theory that people with depression are more vulnerable to cardiovascular problems because their depression raises their risk for hypertension.

Contrary to prevailing opinion, new research indicates it is not depression that raises blood pressure but the drugs used to treat depression—a finding that suggests patients on antidepressants might need to be more closely monitored.

Investigators at the VU University Medical Center, in Amsterdam, the Netherlands, show that depression is associated with low—not high—blood pressure but that taking certain antidepressants, particularly tricyclic antidepressants (TCAs), tends to raise blood pressure and increase the risk for hypertension.

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Does Low Blood Pressure Cause depression?

The Amsterdam study authors speculate on several possible reasons that depressed patients have low blood pressure. First, these patients may be more likely to use medications that treat hypertension, although this study did not find more users of these drugs in the groups with a psychiatric diagnosis, and results were similar when antihypertensive users were excluded from the analyses.

Another explanation could be that both depression and low blood pressure have a common cause. For example, a malfunction in metabolism that increases or decreases levels of certain metabolites, hormones, or neurotransmitters may affect both depression and blood pressure, said lead study author Carmilla Licht.

Perhaps the most likely explanation is that low blood pressure may actually cause depression. People with low blood pressure are often tired, cold, and dizzy and have problems with concentration—symptoms that may cause depression, she said.  She added that the association may go both ways—individuals with low blood pressure may be more likely to become depressed, and those with depression may be more likely to develop low blood pressure.

Some previous research is not in agreement with these results. In fact, some studies found a positive association between depression and high blood pressure. But Licht believes the large sample size of the current study added weight to her results, as did taking into account the use of antidepressants.

What Blood Pressure is considered Very Low?

Blood pressure is a measurement of the pressure in your arteries during the active and resting phases of each heartbeat. Here's what the numbers mean:
  • Systolic pressure. The first (top) number in a blood pressure reading, this is the amount of pressure your heart generates when pumping blood through your arteries to the rest of your body.
  • Diastolic pressure. The second (bottom) number in a blood pressure reading, this refers to the amount of pressure in your arteries when your heart is at rest between beats.

Current guidelines identify normal blood pressure as equal to or lower than 120/80 — many experts think 115/75 is even better.

Although you can get an accurate blood pressure reading at any given time, blood pressure isn't always the same. It can vary considerably in a short amount of time — sometimes from one heartbeat to the next, depending on body position, breathing rhythm, stress level, physical condition, medications you take, what you eat and drink, and even time of day. Blood pressure is usually lowest at night and rises sharply on waking.

What's considered low blood pressure for you may be normal for someone else. Most doctors consider chronically low blood pressure too low only if it causes noticeable symptoms.

Some experts define low blood pressure as readings lower than 90 systolic or 60 diastolic — you need to have only one number in the low range for your blood pressure to be considered lower than normal. In other words, if your systolic pressure is a perfect 115, but your diastolic pressure is 50, you're considered to have lower than normal pressure.

A sudden fall in blood pressure can also be dangerous. A change of just 20 mm Hg — a drop from 110 systolic to 90 systolic, for example — can cause dizziness and fainting when the brain fails to receive an adequate supply of blood. And big plunges, especially those caused by uncontrolled bleeding, severe infections or allergic reactions, can be life-threatening.

Athletes and people, who exercise regularly, tend to have lower blood pressure and a slower heart rate than do people, who aren't as fit. So, in general, do nonsmokers and people who eat a healthy diet and maintain a normal weight.

But in some rare instances, low blood pressure can be a sign of serious, even life-threatening disorders.

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Common Factors Causing Low Blood Pressure and Depression

Various factors are responsible for low blood pressure like dehydration, fatigue, nausea, vomiting, dry mouth, sweating. But there are some other factors due to which depression and low blood pressure may arise- these may include excessive intake of alcohol, severe anxiety or phobia, low levels of potassium in the body. Apart from this adrenal disorders too are responsible for the same.

It is important for people who have been depressed for long to get their blood pressure checked. They may also be feeling lethargic and dehydrated, so such people should opt for tilt table test to check whether they have postural hypotension. If the results of the tests come positive then it is high time to go for complete and proper tests done. You need to immediately consult your doctor.

Medications Cause Low Blood Pressure

Some medications you may take can also cause low blood pressure, including:
  • Diuretics (water pills)
  • Alpha blockers
  • Beta blockers
  • Drugs for Parkinson's disease
  • Certain types of antidepressants (tricyclic antidepressants)
  • Sildenafil (Viagra), particularly in combination with the heart medication, nitroglycerine

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