Do THC and CBD work better together than alone?

The interaction between THC and CBD is complex and context-dependent — not simply additive or synergistic. CBD modulates THC effects through several mechanisms: (1) CBD inhibits CYP2C9 and CYP3A4 enzymes that metabolize THC, increasing THC plasma levels — a pharmacokinetic interaction. (2) CBD acts as a negative allosteric modulator at CB1 receptors, reducing THC's maximal efficacy — potentially reducing psychoactive effects and anxiety. (3) CBD independently activates 5-HT1A, TRPV1, and GPR55 receptors, contributing its own therapeutic effects. Clinical evidence for synergy: the nabiximols (Sativex) 1:1 ratio was chosen partly based on evidence that CBD reduces THC-induced anxiety and cognitive impairment. A 2019 study found 1:1 THC:CBD produced less anxiety than THC alone. However, for some indications (pain, spasticity), THC-dominant preparations may be more effective. The "entourage effect" — broader synergy including terpenes and minor cannabinoids — has theoretical support but limited direct clinical evidence.