In a series of early studies, Jockers-Scherubl and colleagues demonstrated markedly elevated neurotrophins in untreated cannabis-using patients with psychosis compared with both non-using patients and cannabis-using controls: serum nerve growth factor (NGF) and brain derived neurotrophic factor on initial admission (Jockers-Scherübl et al., 2003, 2004). Here, NGF is linked to psychotic disorder.