OPRM1 and Respiratory insufficiency due to muscle weakness: It is well established that activation of mu-opioid receptors can lead to severe respiratory depression (Downes et al., 1967; Dahan et al., 2010), and this is the leading cause of death in the ongoing opioid public health crisis (Dahan et al., 2010; Bedene et al., 2020; Bird and Robertson, 2020).