Inclusion Criteria:  a diagnosis of schizophrenia, schizoaffective disorder, schizophreniform disorder, schizophreniform disorder or psychotic disorder not otherwise specified ability to give informed consent S-25(OH)D< 75nmol/L  Exclusion Criteria:  psychotic symptoms with organic etiology severe mental retardation (IQ<70) hyperparathyroidism hypercalcemia renal failure (s-creatinine levels above 90µmol/L in women and above 105µmol/L for men) pregnancy