The present invention relates to the use of cannabidivarin (CBDV) in the treatment of autism spectrum disorder (ASD) and ASD-associated disorders such as Fragile X syndrome (FXS)； Rett syndrome (RS)； or Angelman syndrome (AS). In a further embodiment the invention relates to the use of CBDV in the treatment of schizophrenia. CBDV has been shown to be particularly effective in improving cognitive dysfunction in rodent models of ASD, FXS, RS, AS and schizophrenia. The CBDV is preferably substantially pure. It may take the form of a highly purified extract of cannabis such that the CBDV is present at greater than 95% of the total extract (w/w) and the other components of the extract are characterised. Alternatively, the CBDV is synthetically produced.
