St. John's Wort and Anxiety: Understanding the Paradoxical Effect

St. John's wort (Hypericum perforatum) is widely used for mild-to-moderate depression, but anxiety is a documented side effect, occurring in 5–15% of users in clinical trials.

Mechanism

Hyperforin and other constituents induce CYP3A4, CYP2C9, and P-glycoprotein, accelerating metabolism of many drugs. They also modulate serotonin, GABA, glutamate, and HPA axis—pathways involved in both mood and anxiety regulation. The net effect can be anxiolytic for some, anxiogenic for others.

Typical Presentation

• Jitteriness, restlessness, insomnia
• Increased worry, panic-like symptoms
• Onset: days to weeks after starting; dose-related

Risk Factors

• Pre-existing anxiety disorder
• High doses (>900 mg/day standardized extract)
• Concurrent stimulants (caffeine, ADHD meds)
• Rapid titration

Clinical Guidance

1. Screen for anxiety before initiating.
2. Start low (300 mg/day), titrate slowly.
3. If anxiety emerges: reduce dose, switch to evening dosing, or discontinue.
4. Do not combine with SSRIs/SNRIs (serotonin syndrome risk).
5. Monitor for drug interactions (OCPs, anticoagulants, antiretrovirals, transplant drugs).

For anxiety disorders, evidence-based first-line treatments include CBT, SSRIs, and SNRIs—not St. John's wort. Always disclose supplement use to your prescriber.