COMT and Mental deterioration: Although we did not observe a direct effect of COMT on cognition, the observation that those who accumulated more iron in DLPFC also showed downtrending changes in working memory among Val carriers can be interpreted as an emerging effect of COMT. In Val carriers, the negative association between iron accumulation and working-memory change might reflect impending working-memory decline, similarly to cognitive decline among Val carriers reported in previous studies (De Frias et al., 2004, 2005).