The use of prescribed steroids, including inhalers, is linked to changes in the structure and volume of white and grey matter in the brain, finds a new study.

The study, published in the journal BMJ Open, indicates that the associations found might help to explain the neuropsychiatric effects, such as anxiety, depression, mania, and delirium frequently seen after long-term use, say the researchers.

"This study shows that both systemic and inhaled glucocorticoids are associated with an apparently widespread reduction in white matter integrity, which may in part underlie the neuropsychiatric side effects observed in patients using glucocorticoids," said researchers, including Merel van der Meulen from Leiden University Medical Center.

Their immunosuppressive properties mean that glucocorticoids, a class of synthetic steroids, are among some of the most frequently prescribed drugs. They are used to treat a wide variety of medical conditions.

Previously published research suggests that long-term medical steroid use is associated with structural abnormalities and shrinkage of certain brain areas. But most of these studies have involved only small numbers of people with specific conditions.

For this study, the team drew on data, comprising half a million 40-69-year-olds from the general population to see if there were any detectable differences in brain volume and structure between users and non-users of systemic and inhaled steroids.

The MRI brain scans of 222 people using systemic steroids and 557 using inhaled steroids were compared with those of 24,106 non-users. None of the study participants had previously been diagnosed with neurological, psychiatric, or hormonal (endocrinological) disorders or was taking mood-altering drugs, such as antidepressants.

A comparison of the MRI scan results showed that systemic and inhaled steroid use was associated with less intact white matter structure than was seen on the scans of those, not on these drugs. White matter has a role in neuronal connectivity and signalling in the brain.

The effects were greater in systemic users than in users of inhaled steroids. And further detailed analysis suggested that the effects might be even larger among long-term users.