Steroids can change the structure of the brain, according to a new study into the commonly-prescribed drugs.
Brain scans of nearly 25,000 people revealed patients taking glucocorticoids had less white matter — the tissue that connects areas of the brain.
Dutch academics said their ‘remarkable’ findings may explain the drugs’ links with neurological problems.
Asthma, arthritis and eczema patients are all routinely prescribed steroids. But well-known side effects include anxiety, mood swings and depression.
Dutch researchers, who studied the brains of nearly 25,000 people, found that those taking glucocorticoids had differences in their brain’s white and grey matter. Those who took the drugs — as tablets, injections or inhaled — had changes in parts of the brain involved with cognition and emotional processing
WHAT ARE GLUCOCORTICOIDS?
Glucocorticoids are a class of steroids taken by one per cent of people in the UK and US.
Common types of the drug include asthma medication beclomethasone, arthritis drug betamethasone and eczema treatments betamethasone and cortisone.
The drugs are classed as either inhaled or systemic, with the latter including those that are taken in tablets or injected.
They are effective at reducing inflammation and suppressing the immune system.
But dozens of studies have linked glucocorticoids with serious side effects, such as high blood pressure, diabetes and weakened bones.
Earlier research also suggested the drugs trigger structural changes and shrink certain areas of the brain. But these only involved small numbers of people.
Although never proven, steroids themselves are widely thought to be behind the crippling symptoms.
The new study, published in the BMJ Open, doesn’t definitively prove the medicines are to blame.
However, the evidence from Leiden University experts provides a potential mechanism that could explain the side effects.
Professor Onno Meijer and colleagues said it was ‘likely’ that glucocorticoids cause changes in the brain.
More research is needed to confirm the results, given that the exact consequences of the changes remain a mystery.
But they argued the findings may, in part, ‘underlie the neuropsychiatric side effects observed in patients using glucocorticoids’.
One in 200 people in wealthy countries take glucocorticoids, rising to one in 100 in the UK and US.
Common types include beclomethasone (asthma) and betamethasone (arthritis).
The drugs are classed as either inhaled or systemic, with the latter including tablets or injections.
They work by suppressing the immune system, which become over-active and causes conditions including arthritis, asthma and eczema.
Researchers examined data on 24,885 people included in the UK Biobank.
The database contains health data on half a million Britons, who underwent dozens of scans and were quizzed on their lifestyle.
Some 222 volunteers used systemic steroids, 557 took inhaled steroids and 24,106 were not taking any steroids.
None had been diagnosed with neurological conditions or were on mood-altering drugs, such as antidepressants.
Professor Meijer and team compared the participants’ MRI brain scans and mood questionnaires.
Steroid users had ‘less intact’ white matter, compared to participants not taking the drugs.
Taking glucocorticoids for the long-term and having the drugs in tablets or injection form, rather than inhaled versions, was linked with the biggest drop in white matter.
Systemic users had a larger caudate, compared to those who were not using the drug.
Meanwhile, those taking inhaled steroids had a smaller amygdala.
Both the caudate and amygdala are involved in cognitive and emotional processing.
Those who used systemic steroid also performed worse on a test that measured their processing speed than non-users.
And they had higher rates of depression, restlessness and fatigue than non-users.
Inhaled steroid users reported only more tiredness than non-users.
The team noted that participants were only asked a few questions on their mood and lower levels of happiness may have been down to their medical condition, rather than the drugs prescribed to treat it.