Passionflower

Passionflower has good evidence as a mild anxiolytic/sedative and for improving sleep in short-term studies, and plausible mechanisms (GABAergic effects, flavonoids, possible effects on circadian genes). There is little-to-no direct, high-quality evidence specifically showing it treats Seasonal Affective Disorder (SAD). If you or someone has SAD symptoms, follow guideline therapies (light therapy, CBT, or antidepressants) and discuss any herbal use with a clinician.

easons passionflower could plausibly help SAD symptoms:

• Anxiolytic / sedative action (GABAergic): Passionflower extracts increase GABAergic signalling in animal and cellular studies and several human trials show reductions in anxiety and sedation without strong cognitive impairment. That calming/sedative effect could indirectly help SAD symptoms (sleep, anxiety, low mood). MDPI
• Flavonoid constituents (apigenin, vitexin, isovitexin, etc.): These flavonoids are bioactive and are thought to mediate the anxiolytic/sedative properties. MDPI
• Possible circadian / clock-gene effects: Preclinical work (and at least one small translational study) suggests passionflower extracts can influence expression of clock genes (e.g., Per2) in cells and animal models — a plausible link to circadian regulation, which is central to SAD. This is suggestive but not proven in humans with SAD. Functional Food Center

Summary: the pharmacology supports anxiety/sleep benefits and a possible circadian effect, so passionflower could help SAD-related insomnia and anxiety symptoms — but that is a mechanistic plausibility, not proof that it treats SAD itself. MDPI

Regulatory / monograph dosing (Health Canada & EMA summaries):

• Health Canada monograph (Passiflora incarnata) lists 0.25–8 g of dried herb per day (depending on preparation) for adolescents 12+ and adults; infusions/decoctions: 1–8 g dried herb/day; take ~1 hour before bedtime for sleep use. (This is a regulatory monograph for traditional use — not an efficacy guarantee.) Health Canada

Doses used in clinical trials (examples)

• Preoperative / dental anxiety trials: single oral doses in trials vary (examples: 260 mg, 500 mg, 700 mg single doses given 30–120 minutes before procedures) and these trials showed reductions in acute procedural anxiety comparable to benzodiazepines in some studies. MDPI
• Sleep studies / teas: low-dose preparations such as 250 mL of passionflower tea in the evening were used in small trials showing modest sleep improvements. Verywell Health

Typical commercial/consumer dosing (what you’ll commonly see)

• Commercial preparations commonly contain 250–900 mg of standardized extract per dose; some sources cite 500–1,000 mg three times daily as therapeutic ranges used in herbal practice (these ranges are broadly used in herbal medicine but are not universally standardized). Start low and follow product label or a clinician’s guidance. Verywell Health

If someone wants to try it for SAD-related sleep/anxiety (note: not a guideline-recommended SAD primary therapy):

• Use a standardized product from a reputable manufacturer.
• Follow label dosing or the Health Canada monograph range; for sleep, many practitioners recommend taking the product ~1 hour before bedtime. For daytime anxiety you may see single doses 30–120 minutes before the anxiety-provoking event in trials. Do not exceed product recommendations without medical advice. Health Canada

Systematic review (best single overview):

• Nutrients (2020) systematic review — “Passiflora incarnata in Neuropsychiatric Disorders”: looked at randomized trials (9 RCTs through Oct 2019). Most trials targeted anxiety (incl. preoperative/dental anxiety) and sleep, with generally positive results for reducing acute anxiety and improving sleep, and no major safety signals in short-term trials. The review authors concluded passionflower may help some neuropsychiatric symptoms but stressed heterogeneity and small study sizes. MDPI

Randomized controlled trials (examples):

• Dental/third-molar anxiety trials (randomized, double-blind): trials comparing Passiflora incarnata (260–500 mg) to midazolam or placebo showed reduced procedural anxiety and less cognitive impairment than benzodiazepines in some studies. Example: Clinical Oral Investigations (2020) study comparing 500 mg Passiflora vs midazolam in third-molar extraction. SpringerLink
• Preoperative anxiety trials: single-dose formulations (260–700 mg) given before spinal/dental/surgical procedures reduced anxiety in randomized settings. The trials are typically short-term (single dose / day-of-surgery) and focused on acute anxiety, not long-term mood disorders. MDPI
• Sleep and stress trials: randomized trials and small multi-center studies report improved sleep quality and reduced stress in short-term use (days–weeks). A randomized trial of passionflower tea vs placebo showed modest sleep improvement in one small study. Verywell Health