Taking oral or inhaled steroid medications for asthma, allergies, or autoimmune diseases appears to produce negative effects on the white matter of the brain. In the study, published in the journal BMJ Open, Dutch researchers found the greatest amount of white matter damage in people who use oral steroids regularly over long periods of time. They had slower mental processing speeds, and more depression, fatigue, and apathy, than people who didn’t use these steroids. People who used inhaled steroids showed less reduction in white matter brain integrity. If you take these medications on a regular basis, it’s important you talk to your doctor and take them only as recommended, ideally at the lowest possible dose to control your illness.