Methods for diagnosing and treating autism spectral disorders are encompassed. In one embodiment, a patient is diagnosed as having autism spectral disorder if at least one CNV in an mGluR network gene is found in a patient sample. Patients with at least one mGluR network gene CNV are effectively treated with (+) - 5-oxo-Dprolinepiperidinamide monohydrate (NS-105) (also known as NFC-1 or fasoracetam).