Limonene is a naturally occurring organic compound found in the peel of citrus fruits such as oranges, lemons, and grapefruits. Like alpha-pinene and beta-pinene, limonene has been studied for its potential effects on the nervous system.

Some studies have suggested that limonene may have beneficial effects on mood and stress levels. A study published in the Journal of Alternative and Complementary Medicine found that inhalation of limonene vapor reduced stress levels in healthy adults, and another study published in the journal Nutritional Neuroscience found that oral administration of limonene improved mood in healthy adults (Lehrner et al., 2005; Komiya et al., 2006).

In addition to potential mood and stress benefits, some studies have also suggested that limonene may have neuroprotective effects. A study published in the journal PLoS One found that limonene had neuroprotective effects in a mouse model of Alzheimer’s disease, and another study published in the journal Life Sciences found that limonene had antioxidant and anti-inflammatory effects in the brains of rats (Oliveira et al., 2016; Lu et al., 2016).