Earlier studies reported increased anandamide (AEA) concentrations in blood samples from schizophrenia patients. AEA levels appeared to normalize in the group of schizophrenia patients who were prescribed typical D2 blocking drugs. There have been several animal studies in which forebrain AEA levels were measured following treatment with psychostimulants or direct dopamine receptor agonists. In the most recently published study there was a decrease in CB1 receptor density in anti-psychotic-treated schizophrenia patients, whereas untreated patients showed no differences from controls. Overall, it is unclear whether CB1 receptor density is altered in schizophrenia: inconsistency dominates. Future studies will take advantage of newly developed radioligands to assay CB1 receptor availability in vivo. Measurement of endocannabinoid (eCB) levels has yielded more consistent data. Raised AEA in schizophrenia has been a replicable observation. So far, it has been claimed that elevated AEA constitutes a protective response.