This is a study of the methods used in assessing clients’ ability to function in Rehabilitative Opioid Substitution Treatment Unit of Substance Abuse Service in Helsinki Deaconess Institute. The main purpose was to survey the existing assessment methods used by the unit’s health care professionals, and to find out in which components of ability to function further evaluation is needed. Also multi-professionally usable assessment methods were considered. The results of this thesis can be utilized by the employees of the Rehabilitative Opioid Substitution Treatment Unit. The thesis can also benefit health care professionals who are interested in this topic and students in need for information about substance abuse services.

The qualitative interview material was analyzed theoretically based on the Canadian Model of Occupational Performance and Engagement (CMOP-E). Furthermore, in this thesis the knowledge of intoxicants and substance rehabilitation is utilized, mainly focusing on opioids. We gathered the data for this study by interviewing six (6) health care professionals at the Rehabilitative Opioid Substitution Treatment Unit of Helsinki Deaconess Institute. The new assessment methods were searched from books and online sources.

The results showed that the most requested outcome was a new method for assessing client’s cognition. It was also discovered that currently the structured methods available for the unit’s health care professionals were mainly focused on individual’s physical and affective component and the cognitive component was assessed to a lesser extent. As a result we found that the unit needed a structured method that was not entirely self-evaluated by the client. The new assessment methods suggested for the use of the unit were the Montreal Cognitive Assessment (MoCA) and the Clock Drawing Test.

Regardless of the occupational therapist’s work field substance abuse is often connected to their clients’ life. Clients with substance abuse-related problems also need different kinds of health care and rehabilitation services. We emphasize that more research about occupational therapy within substance abuse services is needed. Interesting topics could be found in occupational therapy practices within outpatient care. Also a survey of new multi-professionally usable assessment methods would provide valuable information for substance abuse rehabilitation.