Computer training that reduced cannabis approach bias didn't change brain cue responses in teens | Research

The takeaway

Although a computerized approach avoidance training reduced cannabis use in a larger trial, brain imaging in a subsample of 37 youth showed no significant changes in neural cannabis cue reactivity, with only trend-level decreases in amygdala and prefrontal activation.

Researchers studying addiction interventions, clinicians interested in cognitive bias modification, and neuroscience of behavior change.

Training reduced cannabis use but didn't significantly change brain cue responses (d=0.36-0.48)

What the researchers found

CAAT training shifted approach bias toward avoidance while sham training increased approach bias (trend p=0.055). However, no significant neural changes emerged on fMRI between CAAT and sham groups. Small-to-medium effect sizes were observed for decreased amygdala (d=0.36) and medial prefrontal (d=0.48) activation to cannabis cues in the CAAT group.

Why it matters

Computer-based interventions are attractive because they're scalable and cheap. While this particular approach reduced cannabis use behaviorally, the brain mechanism appears not to involve changes in cue reactivity, meaning the intervention may work through other neural pathways.

The numbers in context

37 youth completed all sessions with usable imaging. CAAT: n=19, sham: n=18. Approach bias shift: trend p=0.055. No significant fMRI changes. Effect sizes: amygdala d=0.36, mPFC d=0.48 (small-to-medium, non-significant).

How the study worked

Sub-study of a larger RCT: 37 cannabis-using youth (ages 17-21) completed pre and post fMRI scans around 6 sessions of CAAT (n=19) or sham training (n=18), with cannabis cue reactivity task.

What this study cannot tell us

Very small neuroimaging subsample (n=37). The larger trial showed behavioral effects; the subsample may have been underpowered to detect neural changes. Only examined cue reactivity; other neural measures might show changes. Non-treatment-seeking sample.

How to read the evidence

Preliminary: small randomized substudy nested within a larger RCT, with non-significant primary outcomes.

When this study was published

Published in 2019.

The bigger picture

This is an honest null result. The intervention worked clinically (in the larger trial) but not through the hypothesized brain mechanism (cue reactivity). This kind of finding is crucial for understanding which component of treatment actually drives behavior change.

Questions still open

Through what neural mechanisms does approach avoidance training reduce cannabis use if not cue reactivity? Would more training sessions produce neural changes? Could combining CAAT with other interventions amplify both behavioral and neural effects?

Common questions

Can computer training help teens use less cannabis?

The larger trial found yes, approach avoidance training reduced cannabis use. But this brain imaging substudy found the training didn't significantly change neural responses to cannabis cues, suggesting the behavioral benefit works through a different mechanism.

Why didn't the brain changes match the behavioral changes?

Either the study was too small to detect real but subtle neural changes, or the training works through pathways other than cue reactivity. The small-to-medium effect sizes in the amygdala and prefrontal cortex suggest some signal that larger studies might confirm.

Read the original research

Preliminary evidence that computerized approach avoidance training is not associated with changes in fMRI cannabis cue reactivity in non-treatment-seeking adolescent cannabis users.

Drug and alcohol dependence, 200, 145-152

View on PubMed ↗Publisher’s paper ↗

Citation

Karoly, Hollis C; Schacht, Joseph P; Jacobus, Joanna; Meredith, Lindsay R; Taylor, Charles T; Tapert, Susan F; Gray, Kevin M; Squeglia, Lindsay M. (2019). Preliminary evidence that computerized approach avoidance training is not associated with changes in fMRI cannabis cue reactivity in non-treatment-seeking adolescent cannabis users.. Drug and alcohol dependence, 200, 145-152. https://doi.org/10.1016/j.drugalcdep.2019.04.007