Reviewed: Martínez-Rodríguez A, Martínez-Olcina M, Mora J, Navarro P, Caturla N, Jones J. Anxiolytic effect and improved sleep quality in individuals taking Lippia citriodora extract. Nutrients. January 2022;14(1):218. doi: 10.3390/nu14010218.
By Shari Henson
Chronic anxiety can affect a person’s daily activities and lead to the development of other conditions, such as depression, drug abuse, cardiovascular disease, and insomnia. Researchers have investigated botanical-based treatments for anxiety, which may have fewer adverse effects than some anti-anxiety pharmaceuticals.
Lemon verbena (Aloysia citrodora syn. Lippia citriodora, Verbenaceae) leaves have been used to treat various conditions, including insomnia and anxiety. Verbascoside, the most abundant polyphenol found in lemon verbena, has been shown to exhibit antioxidant, anti-inflammatory, and antimicrobial effects. In animal studies, this compound helped promote sleep and alleviate anxiety. Because few human clinical studies have assessed the effects of lemon verbena on anxiety or sleep, these authors conducted a randomized, double-blind, placebo-controlled clinical trial to assess the effectiveness of a lemon verbena extract commercially known as PLX® or RelaxPLX® (Monteloeder SL; Elche, Spain) in people with high levels of perceived stress and poor sleep quality.
Participants were recruited from several health care centers in Elche, Spain, during 2021. They were 21 years or older, had no chronic pathology, and had a score on the Perceived Stress Scale (PSS) greater than 15 (indicating moderate levels of stress) and a score on the Pittsburgh Sleep Quality Index (PSQI) greater than 5 (indicating poor sleep quality).
Forty participants were assigned randomly and equally to a placebo group or a treatment group. The active treatment used in the study contained a purified extract of lemon verbena leaves standardized to a minimum of 28% total phenylpropanoids, with a verbascoside concentration of at least 24%. Each treatment capsule contained 400 mg of the lemon verbena extract and 150 mg of microcrystalline cellulose. The placebo was 550 mg of microcrystalline cellulose. The participants were instructed to take one capsule daily, one to two hours before bedtime. The intervention period was two months with a one-month follow-up period.
During each of the three study visits (at baseline, after one month, and after two months), weight, height, systolic and diastolic blood pressure, and body composition were measured. Stress and sleep quality questionnaires were completed, levels of the stress hormone cortisol were measured, and an electrocardiogram was performed on each participant. Each participant also wore a Fitbit monitoring bracelet for a seven-day period at the start of each timepoint (at baseline, after one month, and after two months) to assess sleep-related parameters. At the follow-up visit one month after the end of the intervention, participants again answered the questionnaires.
The mean age of participants in the placebo group was 43.4 ± 13.9 years; participants in the intervention group were aged 34 ± 6.28 years. No significant changes were observed in body weight, body mass index, or fat mass in either group.
After one month, stress levels were similar between the two groups. However, after two months, stress significantly decreased by 10.7% in the intervention group compared with baseline (P < 0.05). After the follow-up period, stress scores continued to decrease in the intervention group by 20.5% compared with baseline (P < 0.05). A slight tendency for a decrease in stress was seen in the placebo group compared with baseline, but it was not statistically significant.
Cortisol levels decreased in both the placebo (P < 0.001) and intervention (P < 0.01) groups after one month. However, after two months, cortisol levels increased in the placebo group, reaching similar levels to those observed at baseline, while they continued to decrease by 15.6% in the intervention group (P < 0.001).
PSQI scores significantly decreased after one month and continued to decrease after two months in the intervention group compared with baseline (P < 0.05). By the end of the follow-up period, the scores were 25.9% lower than at baseline. No significant differences were observed in the placebo group throughout the study. The improvements in PSQI scores in the intervention group were greater in females than in males.
According to the Fitbit data, the only significant change in the placebo group was a decrease in the number of times awakened during the night after one month (P < 0.05) compared to baseline. Rapid eye movement (REM) sleep increased significantly in the intervention group compared with the placebo group after two months (P < 0.05). Also, after two months, the number of times awakened during the night decreased, and the time spent in deep sleep increased in the treatment group compared with baseline (P< 0.05 for both).
A potential limitation of this study is the use of the Fitbit, which some researchers consider to have limited accuracy in measuring sleep. The authors concluded that “the consumption of a lemon verbena extract purified in verbascoside has been clinically proven to help reduce anxiety and improve quality of sleep.”