How low blood pressure could be to blame for depression

SCIENTISTS have discovered having low blood pressure could increase the risk of depression by nearly a third.

A study shows patients with lower than normal blood pressure may be 30 per cent more likely to become depressed than those with healthy or even high readings.

The surprising findings, from researchers at Trinity College, Dublin, suggest some cases of depression may be due to reduced blood flow to the brain caused by low blood pressure (or hypotension).

If further studies confirm the link, researchers believe it might be possible to treat depressed patients who also have hypotension by increasing their blood pressure.

The rise in depression diagnoses has led to a massive uptake of drugs such as Prozac, known as selective serotonin reuptake inhibitors (SSRIs). They are thought to improve mood by raising levels of the ‘feelgood’ chemical serotonin in the brain.

But the discovery that low blood pressure could be linked to depression means patients might in future be able to avoid SSRIs and be given drugs or other strategies for low blood pressure.

These might include drinking more water, eating more salt (because it increases blood pressure by retaining fluid in the body) or taking medicines — such as the steroid fludrocortisone — which also help the body retain fluid.

One in ten people in England experiences depression at some point. Some 61 million antidepressant prescriptions were issued in England in 2015 — more than twice as many as ten years ago.

Blood pressure is measured by testing systolic pressure (the top reading, which measures the force generated by blood when the heart beats) and diastolic pressure (the force between beats).

According to the charity Blood Pressure UK, a healthy reading is around 120/ 80. Those scoring 140/90 or more are at increased risk of heart attacks and strokes.

But the latest study suggests low average readings may be bad news for mental health.

The Irish researchers tested more than 4,500 men and women aged over 50 for two years. Each had their blood pressure checked at the start of the study and their mental health assessed using a depression scoring system. Those with existing signs of depression or who were taking antidepressants were excluded so as not to skew the findings.

The rest were tested after two years and the results, published in the journal Age and Ageing, showed around 200 went on to develop depression. Those with systolic blood pressure readings consistently below 130 at the beginning were 30 per cent more likely to have mental health problems. The researchers reported: ‘ Hypotension may represent a modifiable risk factor for depression.’

The findings back up a huge study carried out in Scandinavia which found similar results across all age ranges.

In 2007, researchers at the Norwegian Institute of Science and Technology tracked 60,000 men and women aged 20 to 89, measuring blood pressure and tracking their mental health status over several years. The results, published in the Journal of Epidemiology and Community Health, revealed that those with low blood pressure were 31 per cent more at risk of anxiety and 22 per cent more likely to develop depression than those with healthy blood pressure.

The Norwegian team said low blood pressure may upset the balance of hormones needed to avoid anxiety or depression.

THE study was the first to spot links between low blood pressure and mental health problems in such a large population.

As a result, the American Heart Association now includes depression as one of the signs of low blood pressure. Sandosh Padmanabhan, a retired professor of cardiovascular genomics and therapeutics at the University of Glasgow, carried out a study last year, published in the journal Hypertension, which showed that patients taking beta blockers or calcium channel agonists — which both lower blood pressure — had twice the risk of being admitted to hospital with a mood disorder such as severe depression.

But despite the apparent link, he says it’s too early to say for sure that having low blood pressure can cause depression.

Professor Padmanabhan told Good Health: ‘ The latest study shows that people who have low blood pressure tend to score towards depression on a simple questionnaire.

‘It does not show that low blood pressure causes depression.’

Stephen Buckley, head of information at the mental health charity Mind, said: ‘These initial findings are interesting and highlight an area worth exploring.’