17q12 microdeletions are associated with neurocognitive and developmental involvement of variable severity. Some have mild to moderate intellectual disability; however, such impairment is not universal. Average intelligence is in the average to low average range. Speech delay is common, regardless of intellectual functioning. The most striking association between 17q12 microdeletions and neurodevelopment is the raised prevalence of autism spectrum disorder, with significant increases in both diagnosis and subclinical autistic traits. 17q12 microdeletions have been implicated as one of the major genetic causes of high-functioning autistic spectrum disorders. Schizophrenia is also a significant psychiatric complication of 17q12 microdeletion syndrome. 17q12 microdeletions are estimated to occur in approximately 1 in 1,600 people with schizophrenia, compared to an estimation of below 1 in 50,000 in the general population. Epilepsy, usually mild, occurs in approximately one-third of cases.