Additional analyses did not reveal significant differences in demographic (i.e. sex, education years, age at scan; supplementary Table 5), global cognitive (i.e., ACE total score), clinical (i.e., disease duration) or schizotypal (i.e., all three SPQ subdomain scores) characteristics between diagnostic subgroups with C9orf72 repeat expansion, suggesting that the C9orf72 subanalysis results are unlikely to be driven by any of the diagnostic groups and representative of the ALS–FTD spectrum. This evidence concerns the gene C9orf72 and frontotemporal dementia.