Methods are disclosed for decreasing stem cell proliferation, including cancer stem cell proliferation. These methods comprise administering to stem cells inhibitors of AMP activated protein kinase (AMPK). Methods for promoting stem cell growth by increasing stem cell proliferation, self-renewal and/or differentiation are also disclosed. These methods comprise administering AMPK activators to stem cells. Methods of achieving selective differentiation of stem cells are also disclosed. These methods comprise administering small molecules to stem cells that modulate AMPK activity. Applications of these methods are also disclosed, such as methods of increasing numbers of neuronal progenitor cells. These methods can be used therapeutically, such as for repair of spinal cord injuries, or for stimulating neurogenesis in the hippocampus, and other cell-based therapies. The methods can also be used for screening of compounds that can be activators or inhibitors of AMPK activity.