A very close friend has an addiction to marijuana. How can I step in this personal issue?

A very close friend has an addiction to marijuana. How can I step in this personal issue? I live in Clarks Green, Pennsylvania. Which government or voluntary or professional group would help me with this?

: http://alcoholdrugstreatment.info/a-very-close-friend-has-an-addiction-to-marijuana-how-can-i-step-in-this-personal-issue