Beyond Usage Time: Rethinking Therapeutic Dose and Effect in Digital Therapeutics

Area of Science:

• Digital Health
• Mental Health Interventions
• Behavioral Science

Background:

• Digital therapeutics (DTx) are increasingly used for mental health care, offering scalable, evidence-based solutions.
• A common assumption is that longer usage time in DTx directly correlates with better therapeutic outcomes, mirroring pharmacotherapy dose-response models.

Purpose of the Study:

• To critically evaluate the assumption that increased usage time is essential for therapeutic success in digital mental health interventions.
• To explore factors complicating linear dose-response models in digital therapeutics.
• To advocate for a shift in evaluation frameworks for digital mental health interventions.

Main Methods:

• Review of psychotherapy dose-effect research.
• Analysis of findings from digital intervention trials.
• Incorporation of empirical work on user engagement and outcomes.

Main Results:

• The relationship between usage time and clinical benefit in digital mental health is complex, not linear.
• Factors such as early response, user heterogeneity, motivation, context, and off-platform skill use challenge simple dose-response models.
• Usage time is an imperfect proxy for therapeutic engagement and intervention quality.

Conclusions:

• Equating greater usage time with greater effectiveness risks conflating exposure with therapeutic mechanisms.
• Current evaluation frameworks may prioritize duration over meaningful therapeutic change.
• A shift towards mechanism-informed, individualized evaluation focusing on the quality, timing, and functional impact of intervention use is needed.