1. generally, any action intended to interfere with and stop or modify a process, as in treatment undertaken to halt, manage, or alter the course of the pathological process of a disease or disorder.

2. action on the part of a psychotherapist to deal with the issues and problems of a client. The selection of the intervention is guided by the nature of the problem, the orientation of the therapist, the setting, and the willingness and ability of the client to proceed with the treatment. Also called psychological intervention.

3. a technique in addictions counseling in which significant individuals in a client’s life meet with him or her, in the presence of a trained counselor, to express their observations and feelings about the client’s addiction and related problems. The session, typically a surprise to the client, may last several hours, after which the client has a choice of seeking a recommended treatment immediately (e.g., as an inpatient) or ignoring the intervention. If the client chooses not to seek treatment, participants state the interpersonal consequences; for example, a spouse may be request that the client move out, or the client’s employment may be terminated.

4. a similar confrontation between an individual and family and friends but outside of the formal structure of counseling or therapy, usually over similar issues and with the goal of urging the confronted individual to seek help with an attitudinal or behavioral problem. Also called family intervention.

5. in research design, an experimental manipulation. —intervene vb.