The influence of client behavior during motivational interviewing on marijuana treatment outcome.

Psychotherapy process research continues to be important in identifying within session client and therapist behaviors related to outcome. Motivational Interviewing (MI) assumes that the type of client language elicited within session is important. Client behavior was coded from 61 MI sessions with marijuana dependent adults. Sessions were coded for client language using the Client Language and Commitment Scale. Client statements indicating desire and reasons for change were significantly predictive of marijuana treatment outcome through the 34-month follow-up above and beyond baseline levels of marijuana use or motivation for change. Commitment language was not associated with outcomes. These findings suggest specific types of client language statements predict marijuana treatment outcome and are durable to a 34-month follow-up.