Whilst it’s been known for years that lithium drugs help many bipolar patients to manage their disorder, it hasn’t been known how lithium acts. But now there is a clue! Laboratory studies show a link between lithium and an enzyme known as PO*. This enzyme controls a group of genes which affect brain cells’ sensitivity to lithium. And one of those genes, ImpA2, is also associated with bipolar disorder in some sufferers. So possibly there is a functional connection between ImpA2 and bipolar disorder, which can be mediated by lithium. Understanding this link could lead the way to better treatments for bipolar depression.