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The disease has been reported worldwide, but is more frequent in Ashkenazi Jewish populations. The incidence of severe CD in the non-Jewish population has been estimated at approximately 1:100,000 births. If both parents are of Ashkenazi Jewish descent, the incidence is 1:6,400 to 1:13,500 births. The main form of CD is the severe form.

Two forms of CD are clinically distinguishable: severe Canavan disease with onset in the neonatal period or infancy, and mild Canavan disease diagnosed in children (see these terms).In the severe form, patients have severe hypotonia, developmental delay and other neurologic impairments, and a very high N-acetyl-L-aspartic acid (NAA) concentration in urine, blood and cerebrospinal fluid. In mild Canavan disease, there can be mild developmental delay, problems with speech or achievement at school and urine NAA is slightly elevated.

CD is caused by mutations in the ASPA gene (17p13.3), coding for the aspartoacylase enzyme. Numerous mutations have been identified, and subsequent enzymatic activity is either low or totally absent. In Ashkenazi Jews, two common mutations have been identified. Mild forms of Canavan disease are usually compound heterozygotes with one mild and one severe mutation.

Prognosis is variable. In severe Canavan disease, life expectancy is reduced with average survival until 10 years or occasionally longer. In mild Canavan disease, life expectancy is usually normal and the prognosis is good.