Statins can indeed produce neurological effects. These drugs are typically prescribed to lower cholesterol and thereby reduce the risk of heart attack and stroke. Between 2003 and 2012 roughly one in four Americans aged 40 and older were taking a cholesterol-lowering medication, according to the Centers for Disease Control and Prevention. But studies show that statins can influence our sleep and behavior—and perhaps even change the course of neurodegenerative conditions, including dementia.

The most common adverse effects include muscle symptoms, fatigue and cognitive problems. A smaller proportion of patients report peripheral neuropathy—burning, numbness or tingling in their extremities—poor sleep, and greater irritability and aggression.

Interestingly, statins can produce very different outcomes in different patients, depending on an individual's medical history, the statin and the dose. Studies show, for instance, that statins generally reduce the risk of ischemic strokes—which arise when a blocked artery or blood clot cuts off oxygen to a brain region—but can also increase the risk of hemorrhagic strokes, or bleeding into the brain. Statins also appear to increase or decrease aggression.

In 2015 my colleagues and I observed that women taking statins, on average, showed increased aggression; men typically showed less, possibly because of reduced testosterone levels. Some men in our study did experience a marked increase in aggression, which was correlated with worsening sleep.

Statins may also affect neurodegenerative disorders, such as dementia, Parkinson's disease or amyotrophic lateral sclerosis (ALS). For instance, some patients taking statins develop ALS or ALS-like conditions with progressive muscle wasting, which sometimes resolve when the patients stop taking the medication. The drugs may play a role in triggering symptoms, at least in those cases, but may also prevent the progression of such conditions in some settings. One possible explanation is that statins cause increases or decreases in tissue damage known as oxidative stress, involved in neurodegenerative diseases.

The effects of statins are complex. We hope that further study will shed light on the neurological problems statins can cause and explain how to better protect those who experience these troubling complications.

Question submitted by Alan Cleugh, U.K.

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