Abstract: Provided herein are compositions and methods for treating succinic semialdehyde dehydrogenase deficiency (SSADHD). Compositions may include a gene encoding a functional succinic semialdehyde dehydrogenase (SSADH) enzyme, such as ALDH5A1, operably linked to a targeting vector. The functional SSADH enzyme is envisioned to lower the levels of circulating gamma-hydroxybutyric acid (GHB) and ?-aminobutyric acid (GABA). In some embodiments, combination therapies are envisioned, comprising administering to the subject therapeutically effective amounts of a combination of a composition comprising a gene encoding a functional SSADH enzyme operably linked to a targeting vector; one or more mTOR inhibitors; and a GABA-T inhibitor. Suitable mTOR inhibitors include rapamycin, while suitable GABA-T inhibitors include vigabatrin.