NEFL and mild neurocognitive disorder: Elevated NfL levels have been found in numerous neurological conditions from Alzheimer’s disease (AD) to motor neuron disease (MND) (Kuhle et al., 2011; Lu et al., 2015; Rohrer et al., 2016; Byrne et al., 2017; Mattsson et al., 2017; Benatar et al., 2018; Gaetani et al., 2019a; Lin et al., 2019).