Single-participant assessment of treatment mediators: strategy description and examples from a behavioral activation intervention for depressed adolescents.
Track activation each session—when it rises before mood, you have likely found your active ingredient.
01Research in Context
What this study did
Four depressed teens joined a case series. Each teen filled out short mood and activity logs every day.
The team also tracked negative thoughts. They used single-participant mediator tests to see what moved first: activity, thoughts, or mood.
What they found
For two teens, mood lifted only after their daily activity scores rose. Negative thinking never led the change.
The other two teens showed no clear pattern. Activity jumps came first in the kids who got better.
How this fits with other research
Ellingsen et al. (2014) ran the same teen-level mediator logic but watched family conflict instead of activity. They also saw that the chosen target had to move before mood moved.
Hopkinson et al. (2003) earlier showed that reinforcing varied responses brightened mood in college students. Gaynor et al. (2008) extends that idea by proving the change is sequential: more activity, then better mood.
Grindle et al. (2012) later mixed behavioral activation with exposure for veterans. They still kept the core "do more first" rule, showing the idea travels beyond teens.
Why it matters
You can test your own clients in real time. Plot activation and mood each session. If activation climbs first, keep pushing activity. If it does not, switch gears. This quick check saves weeks of guesswork.
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02At a glance
03Original abstract
Determining the means by which effective psychotherapy works is critical. A generally recommended strategy for identifying the potential causal variables is to conduct group-level statistical tests of treatment mediators. Herein the case is made for also assessing mediators of treatment outcome at the level of the individual participant. Single-participant assessment of mediators requires documenting, for each participant, that treatment was received, that change occurred on the mediator and relevant clinical outcome measures, and that the change on the mediator happened at an expected time in the treatment protocol and prior to substantive change on the dependent variable. Data from four depressed adolescents who demonstrated remission following a behavioral activation intervention illustrate the use of the approach in assessing whether changes in activation level or negative thinking mediated the changes in depression. For two participants, increased activation appeared to be a mediator, whereas decreased dysfunctional thinking never emerged as a plausible mediator. It is concluded that single-participant assessment of mediators of treatment outcome offers a useful additional tool for determining possible mechanisms of action in effective psychotherapy.
Behavior modification, 2008 · doi:10.1177/0145445507309028