Neurogenesis is the process where we create new brain cells. Many researchers believe that if someone has depression then neurogenesis is reduced. Could this in some cases even be the cause of depression? It's possible this idea could lead to the discovery of new drugs for depression, drugs which don't tackle mood, but which encourage the creation of new brain cells. Claudia Hammond brought together Timothy Powell, MRC postdoctoral research fellow, and Sandrine Thouret, Head of Neurogenesis and Mental Health, from Kings College London to examine the latest research. The Government has committed to make prisons not just places of detention, but of rehabilitation. Some prisons are hoping that yoga classes could make a difference. Research from Oxford University is beginning to suggest that yoga can help with prisoners' mental health. Claudia Hammond hears from lead researcher and psychologist Amy Bilderbeck, Sam Settle Director of the Prison Phoenix Trust and former prisoner Richard for whom yoga was to become a vital tool during his years as an inmate. This week's Insiders' Guides to mental health asks with all the guidance out there in the public domain, how do you decide what is best for you? We hear from Stephen Buckley from Mind, GP Daniel Dietch and before them Lisa Rodrigues, who's had mental health issues herself and long experience of managing services. Psychologists discovered long ago that most of us think we're better than average at most things - the Lake Wobegon Effect - and that we go round looking for information that confirms our views on life - the confirmation biases. But there's now another bias in our thinking. If we imagine a theory is our own, we think it must be true. Aiden Gregg, Associate Professor of Psychology at the University of Southampton, told Claudia Hammond about his new research. Producer Adrian Washbourne.