The diabetes drug metformin not only helps to control blood glucose, it can also encourage the growth of new brain cells. Similar to the way it activates a certain pathway in the liver, metformin can activate neural stem cells to form new brain cells and help repair injured parts of the brain.
Animal studies show that this new brain cell growth also translates into improved cognitive functioning after a brain injury. Other studies with Alzheimer's patients are showing similar benefits, and researchers now hope to begin study for people with traumatic brain injury. The benefit of metformin is that it is already such a widely used drug for diabetes, and its safety and reliability has already been well established.
Wang J, Gallagher D, Cancino GI, et al. Metformin activates an atypical PKC-CBP pathway to promote neurogenesis and enhance spatial memory formation. Cell Stem Cell. (July 2012).