In a study, exercise improves mood partly because it increases endorphin levels. What role does endorphin play?

In a study, exercise improves mood partly because it increases endorphin levels. What role does endorphin play?

• A. Mediator.
• B. Moderator.
• C. Confounder.
• D. Outcome.

Answer: (A)

The key idea is that endorphin acts as a mediator in the pathway from exercise to mood improvement. A mediator is a variable that explains how or why a treatment or behavior has an effect on an outcome—it lies in the causal chain between the two. In this scenario, exercising leads to increased endorphin levels, and the rise in endorphins helps produce the observed improvement in mood. So the endorphin release is the mechanism that transfers the effect of exercise onto mood. This isn’t a moderator, which would be a factor that changes the strength or direction of the exercise–mood relationship depending on its level (for example, a variable that makes the effect stronger for some people but weaker for others). It isn’t a confounder, which would be an outside variable that causes both more exercise and better mood, creating a spurious link. And the mood itself is the outcome, not the mechanism. So endorphin’s role is to mediate the effect—explaining how exercise leads to improved mood.

The key idea is that endorphin acts as a mediator in the pathway from exercise to mood improvement. A mediator is a variable that explains how or why a treatment or behavior has an effect on an outcome—it lies in the causal chain between the two.

In this scenario, exercising leads to increased endorphin levels, and the rise in endorphins helps produce the observed improvement in mood. So the endorphin release is the mechanism that transfers the effect of exercise onto mood.

This isn’t a moderator, which would be a factor that changes the strength or direction of the exercise–mood relationship depending on its level (for example, a variable that makes the effect stronger for some people but weaker for others). It isn’t a confounder, which would be an outside variable that causes both more exercise and better mood, creating a spurious link. And the mood itself is the outcome, not the mechanism.

So endorphin’s role is to mediate the effect—explaining how exercise leads to improved mood.