chronic illness, nutrition, body weight, alcohol and cannabis use, etc. Untangling which epigenetic marks better relate to the causes versus the consequences of illness will be difficult. Indeed, only a fraction of the illness associated CpGs, 4.6%, showed association to nearby genetic variants in the meQTL analysis, further suggesting these findings may be more related to the epiphenomena of the illness state than to the genetic causes of the disorder. Lastly, while these diagnosis-associated CpGs were not confounded by cell composition, it is possible that they have larger effect sizes in individual cellular populations, and new consortia like the psychENCODE project43 can better identify the cellular specificity of, and potentially magnify, these effects.
