ADD1 and Huntington disease: Although in non-HD models, antipsychotics can downregulate UCHL1, clozapine upregulates ADD1, lithium upregulates MTHFR and ADD1, valproate upregulates MTHFR and SKP1A, and fluoxetine upregulates SKP1A transcription while lithium downregulates REST, although these findings have yet to be demonstrated in HD models, let alone in human HD at conventional therapeutic doses.