Comparing Single-Session vs. Multi-Session Exposure Therapy for Specific Phobias

Efficacy vs. Efficiency: The Core Comparison

To evaluate these treatments, researchers look at two distinct metrics: efficacy (how well the treatment works to reduce symptoms) and efficiency (how much time or resources are required to achieve that effect).

In a recent meta-analysis of 67 studies involving 1,758 participants, researchers compared these two approaches using two primary outcome measures:

• Self-reported phobia symptoms (SPS): Subjective measures of fear, such as the Spider Questionnaire.
• Behavioural Approach Task (BAT): Objective measures of approach behavior, such as how close a person is willing to get to a feared stimulus.

The findings were striking. Regarding efficacy, there was no significant difference between single-session and multi-session exposure. Both approaches produced large, significant reductions in phobia symptoms at both post-treatment and follow-up assessments (ranging from 4 weeks to 14 months).

However, regarding efficiency, single-session exposure was significantly superior. The mean total treatment time for multi-session exposure was significantly longer, averaging about 137 minutes more than single-session treatment.

Factors That Influence Treatment Outcomes

While the overall efficacy was similar, the meta-analysis explored several "moderators"—variables that might change how well the treatment works for different people.

Phobia Subtype and Developmental Stage

The specific type of phobia (e.g., animal, situational, blood-injection-injury, or heights) significantly moderated the effect size. For instance, the direction of the association between the subtype and the outcome varied depending on whether the researcher was measuring self-reported fear or actual behavioral approach. Additionally, the researchers examined whether the developmental stage (children/adolescents vs. adults) played a role, noting that exposure therapy has proven effective across both age groups.

Intervention Format and Researcher Allegiance

The study also looked at whether therapy was delivered in a group or individual format. While individual therapy is more common, group settings can increase accessibility and provide peer encouragement. Finally, the researchers investigated researcher allegiance—specifically whether studies conducted by the founders of One-Session Treatment (OST) reported higher success rates than independent studies.

Summary of Findings

The meta-analysis suggests that for clinical populations suffering from specific phobias, the "intensity" of a single session does not sacrifice the quality of the outcome compared to a longer, multi-session course.

Clinical Implication: Because single-session exposure is just as effective but much faster, healthcare policies that facilitate access to intensive, single-session treatments could significantly reduce costs and improve patient access to care.