What is happening. Rhodiola has mild monoamine-modulating, MAO-inhibiting activity and saffron is serotonergic, so combining them adds to overall monoaminergic tone.
Mechanism. Rhodiola constituents weakly inhibit monoamine oxidase and modulate serotonin and norepinephrine; saffron adds serotonergic reuptake modulation, producing additive monoaminergic effects.
Recommendation. Combine only with care, starting at low doses. Avoid if also taking antidepressants or other serotonergic agents, and monitor for overstimulation, restlessness, or agitation.