If you could create a painless, inexpensive cure for a single ailment, what would you cure and why?
Working in mental health I would love to find a cure for low self-esteem. It is at the core of many illness and plays a major role in suicide and self-harm behaviours. Low self-esteem can be improved however it is usually a long, slow journey, which the person living with it struggles to believe is possible to change. This impacts their want to start as it seems to hard. By creating a painless, inexpensive  and quick cure for low self-esteem the impact of mental health would be lessened.
The side effect of being able to cure low self-esteem may be that factors causing low self-esteem such as bullying, abuse, relationship problems, high stress, perfectionism may lessen and stop the cycle repeating itself. Low self-esteem is like a spark that turns into a wild-fire in some people. If it can be limited to back burning in its fire intensity it is much easier to control and many lives would be saved.