Lion's mane mushroom (Hericium erinaceus) has garnered scientific interest for its potential effects on the nervous system, including aspects related to the parasympathetic nervous system (PNS). Several preclinical studies have shown that lion's mane contains compounds, such as hericenones and erinacines, that can stimulate the synthesis of nerve growth factor (NGF), a protein essential for the growth and maintenance of certain types of neurons. Some animal studies suggest lion's mane may enhance vagal (parasympathetic) activity, improve recovery from nervous system injury, and support neuroprotection, which indirectly supports the PNS by promoting nerve health and function.

Human studies, though limited, have primarily focused on cognitive function and mild cognitive impairment, showing modest improvements in memory and mood. While these suggest general nervous system support, direct evidence for specific parasympathetic modulation in humans is lacking. Nonetheless, animal data and mechanistic studies provide a plausible rationale for lion’s mane supporting PNS-related functions, such as mood regulation and stress resilience. Further clinical studies are needed to confirm these effects in humans and clarify the connection to the parasympathetic system.

In summary, there is emerging scientific evidence—mainly from animal and in vitro studies—that lion's mane may support the health of the parasympathetic nervous system, but robust clinical validation is limited at this time.