PRL and Increased circulating prolactin concentration: Whilst hyperprolactinaemia is undoubtedly a side effect of anti-psychotic medication, albeit to varying extents depending on which dopamine receptors are predominantly antagonised, patients at high risk of developing psychosis, and and those with a first psychotic episode, exhibit increased serum PRL concentrations independent of anti-psychotic medication according to a recent meta-analysis [62,63].