Strongest evidence: Lavender shows the most consistent evidence for improved sleep quality, with all 3 available studies reporting moderate beneficial effects in clinical populations, including patients undergoing chemotherapy and postmenopausal women. The most studied form was inhaled lavender oil, with study durations ranging from 5 days to 2 months (median 31 days). Sleep quality improvements were statistically significant across all trials, though the evidence strength is rated low due to small sample sizes and potential publication bias.
Mixed or weaker evidence: For reduced anxiety, 2 of 3 studies reported beneficial effects (one small, one moderate), while 1 was neutral. This evidence is rated low strength and is considered preliminary, with effects observed in narrow populations (postmenopausal women at 500 mg/day oral dose for 8 weeks, and children aged 6–10 years via aromatherapy). Delivery method (oral capsule vs. inhaled) and population differences limit generalizability.
Effective dose patterns: No single effective dose range emerges across both outcomes. For anxiety, the only quantified effective dose was 500 mg/day oral lavender over 8 weeks (small effect). For sleep, inhaled lavender oil was used without a standardized dose, with effects seen after 5 days in one trial and after 31 days (median) in longer studies. No cross-cutting dose range is identifiable.
Population insights: The available research is limited to specific groups. For sleep, clinical populations (e.g., patients with hematological malignancies undergoing chemotherapy) and postmenopausal women show benefit. For anxiety, effects are observed only in postmenopausal women and young children. Applicability to general or other populations remains unclear.
Notable caveats: Both syntheses have small evidence bases (3 studies each), making conclusions preliminary. For anxiety, different delivery methods (oral vs. aromatherapy) may produce different effects. For sleep, publication bias is a concern, as all 3 studies reported positive outcomes. No studies reported harmful effects for either outcome.