More recent research has attempted to address some of the limitations of the early studies on CHRMs in schizophrenia by measuring CHRM1/CHRM4 using SPECT and 123I-IDEX binding in 30 medication-free people who were diagnosed with a psychotic disorder and were in the early phase of the disease (Bakker et al., 2018). Here, CHRM4 is linked to psychotic disorder.