Cognitive disorders (CDs) are a heterogeneous group of disorders for which the genetic foundations are rapidly being uncovered. The large number of CD-associated gene mutations presents an opportunity to identify common mechanisms of disease as well as molecular processes that are of key importance to human cognition. Given the disproportionately high number of epigenetic genes associated with CD, epigenetic regulation of gene transcription is emerging as a process of major importance in cognition. The cognate protein products of these genes often co-operate in shared protein complexes or pathways, which is reflected in similarities between the neurodevelopmental phenotypes corresponding to these mutant genes. Here we provide an overview of the genes associated with CDs, and highlight some of the epigenetic regulatory complexes involving multiple CD genes. Such common gene networks may provide a handle for designing therapeutic interventions applicable to a number of cognitive disorders with variable genetic etiology. This article is part of the Special Issue entitled 'Neuroepigenetic Disorders'.