Lemon balm appears to reduce anxiety substantially, according to a 2021 meta-analysis of randomized clinical trials, although there wasn’t good agreement on the effect size between the studies included in the meta-analysis. Lemon balm may be more effective for immediate or situational (acute) anxiety than for long-term (chronic) anxiety. In the reviewed studies, lemon balm decreased acute anxiety in hospitalized patients with burns, acute coronary artery syndrome, and coronary artery bypass grafts, as well as in teenage girls with PMS, with an overall large effect size; it also decreased chronic anxiety in office workers and hospitalized patients with chronic stable angina, with an overall moderate effect size.[1] However, there was a high risk of bias in most of the studies; more high-quality research is needed.
Based on the available evidence, lemon balm may also be useful for depression. The same 2021 meta-analysis found that there was a moderate reduction in depression with lemon balm. There were only three studies included in the analysis, but all the included studies showed similar results for short-term (acute) and long-term (chronic) depression.[1] Again, more high-quality research is needed to confirm lemon balm’s usefulness for depression.
Lemon balm may also have benefits for sleep quality, especially in the contexts of depression, anxiety, stress, and anxiety-provoking heart conditions (chronic stable angina, benign palpitations, coronary bypass surgery). Multiple studies have evaluated lemon balm’s effect on sleep quality and onset in these contexts, finding that supplementation with lemon balm increased sleep quality scores[2][3][4] and sleep duration,[5] reduced insomnia,[6][7] and hastened sleep onset.[5] These effects may be due to anxiety reduction, as anxiety contributes to sleep problems. To date, the evidence supports the use of lemon balm for sleep in the context of anxiety, stress, depression or anxiety-provoking health conditions, but more research is needed to determine whether lemon balm can help with general insomnia.
Lemon balm has also been studied in combination with other herbs, such as valerian, for sleep;[8][9][10] however, it’s not clear how much of the effect in these trials is due to lemon balm.