As far as purpose 1 goes in my own experience we seem to be nowhere near having a cure for any mental illness.
Sadly, this is something I have to agree with you Tim. Despite how far this field has come, particularly over the past two decades, human mind and behaviour still remains a challenging quest for scholars and scientists. I put this down partly to our individual differences.
I suppose that the day we have the answer for questions such as the one you ask about intrusive thoughts we will have unveiled the fundamentals of consciousness. There are indeed many fascinating assumptions out there; yet, they come with many, many gaps!
All the best to you always Tim.
Thank you so much for taking the time to stop by, read and comment :)