Lemon balm (Melissa officinalis) has a long history of traditional use in Europe for its calming and sedative properties, particularly in the management of sleep disturbances such as insomnia. In more recent decades, its use has been investigated in clinical and preclinical studies, though the evidence base remains modest.

Several small randomized controlled trials and open-label studies have evaluated lemon balm, often in combination with other herbs like valerian. Results from these studies suggest that lemon balm may reduce symptoms of mild insomnia and improve sleep quality. For example, a 2011 pilot study found that a standardized lemon balm extract improved symptoms of insomnia and anxiety in subjects with mild-to-moderate symptoms. However, these studies are generally limited by small sample sizes, short durations, and lack of blinding.

Mechanistically, lemon balm is thought to exert its effects via modulation of gamma-aminobutyric acid (GABA) activity in the brain, which is associated with anxiolytic and sedative effects. Animal studies support this hypothesis, showing that lemon balm extracts increase GABA levels and exhibit sedative properties.

In summary, while there is emerging scientific support for the use of lemon balm in mild insomnia, the quality and quantity of evidence are not sufficient for strong recommendations. More rigorous and larger-scale clinical studies are needed to confirm its efficacy.