I believe some mental conditions do have their positive sides. ADHD, for example, has been thought to be associated with higher IQ's and it often helps a person focus on their interests to the point that they can often make groundbreaking changes. This isn't true of all mental conditions because each condition is unique.
Yes, there is a positive side to mental conditions, because we are not all the same. Some people are crazy, but that makes them spontaneous and fun. We need all kinds and types of people in the world. There is some good to find in most people in the world. We are all special.
There is a positive side to mental conditions. As adverse and negative as it may seem, there are people who perform much better in other areas as a result of a mental condition. I once heard of this artist from New York who drew in pen the entire city of New York from memory, and he suffered from autism.
There are certain mental conditions that give you different strengths that other people may not necessarily have available to them. ADHD, for example, tends to make one be very energetic. Another effect is that it can make one more understanding of others and more sensitive to the idiosyncracies of others.
When it comes to mental conditions, there generally is no positive side, with the exception of the pun, "the manic side" of bi-polar disorder. Mental conditions are often the cause of frustration, improper social attitudes, negative mental thoughts, lack of self-worth, etc. For that reason, there really is no positive side to mental conditions.