ACE2 and schizophrenia: nAChRα7 is widely expressed in neuronal tissue, the digestive tract, and in the lungs and the airways; plays various roles in smoking-related schizophrenia [26] and chronic pulmonary diseases [6]; and is also associated with higher angiotensin-converting enzyme II (ACE-2) expression and subsequent higher risk of severe COVID-19 infection [27,28].