There is evidence that certain risk factors for schizophrenia (e.g. copy number variations, obstetric complications) are associated with an earlier age of onset of psychosis. One possible explanation is that in such cases, early neurodevelopmental damage is associated with greater perturbance of critical neural systems and that this leads to the early presentation of psychosis. Less is known about the significance of age of onset for treatment response and outcome though patients presenting in childhood are reported to have a worse outcome than those who present later. We have conducted two large first episode psychosis studies in which we have examined those baseline characteristics which predict later treatment resistance, notably the AESOP and GAP studies. In each of these, early age of onset and also male gender were associated with treatment resistance. Interestingly in approximately three quarters of cases, treatment resistance was present at onset of psychosis and only in the remaining quarter did it develop over the course of the illness. One possibility is that there exists a type of schizophrenia which is associated with neurodevelopmental damage, early age of onset and lack of response to dopamine blockade; this is compatible with our previous finding that patients with treatment resistant schizophrenia do not show the increased synthesis of striatal dopamine which is usually found in actively psychotic individuals.