To investigate whether anxiety reductions attributed to healing crystals reflect placebo responses driven by conditioning and belief-related biases rather than specific therapeutic effects.

In a randomized, controlled study, 138 adults were classified as believers or nonbelievers in crystal efficacy and assigned to rose quartz (experimental) or a visually matched placebo. Participants followed a standardized 14-day protocol. Anxiety was assessed pre- and post-intervention with the Beck Anxiety Inventory and the Spanish Kuwait University Anxiety Scale. Multilevel analyses of variance (ANOVA) and Bayesian models were used to evaluate main effects, interactions, and evidence for treatment specificity.

Anxiety reductions occurred only among believers, regardless of crystal assignment. No differences were detected between groups in primary outcomes, and improvements did not exceed the magnitudes typically associated with placebo responses. Bayesian estimates favored the null hypothesis for specific treatment effects. Preexisting belief strongly predicted perceived efficacy and symptom change, consistent with causal illusions plausibly shaped by conditioning mechanisms. Nonbelievers showed no reliable improvement.

Healing crystals did not demonstrate anxiolytic effects beyond those of the placebo. Symptom change was mediated by expectancy and conditioning, particularly in individuals inclined toward intuitive or magical thinking. Although nonspecific, context-dependent factors—such as elements of the therapeutic alliance—may amplify placebo responsiveness in clinical settings, these findings do not support attributing inherent therapeutic value to crystals. Future work should delineate how expectations, clinician-patient rapport, and related variables interact to shape placebo response and how such mechanisms might be ethically leveraged to enhance evidence-based care without promoting pseudoscientific practices.