The following sequence:
Next scree: "how are you?" presented with buttons probing for specific symptoms (down, sad, stressed, anxious).
3rd screen - once feeling is established - scene moves on to more specific probes - more buttons to give options for what user feels bad about).
Next screen may include radio buttons to select options to elicit information about exactly what aspects of their problem they feel bad about.
Next screens provide conditional statements based on what user has reported. Derived from dense database. I envisage this being the biggest challenge.