How can I proof?

Hi,
I want to proof that someone can stop smoking weed without any need of a psychiatrist or psychologist.
What I want to proof (evidence or studies showing this would be helpful) is that one can stop smoking any time, as long as the will and the need is there.

Please help!

Any evidence or studies showing this will be very helpful since I can present them in the court of law about the custody of my child.

Thanks