The fragile X mental retardation gene, FMR1, contains a polymorphic CGG repeat in the 5′-untranslated region of exon 1. Once unstable, this repeat is capable of expansion across generations. Women who carry a premutation allele (55–199 repeats) are at risk of passing on a full mutation allele (>200 repeats) to their offspring. A full mutation leads to the most common form of inherited intellectual disability, fragile X syndrome (FXS). Mounting evidence suggests that premutation carriers may be vulnerable to symptoms of anxiety and depression. The goal of this study was to test the hypothesis that among women who carry a premutation, the stress of raising a child with FXS would be moderated by genetic factors influencing endogenous cortisol responses, which could in turn modulate anxiety and depression symptoms. To this end, we genotyped single nucleotide polymorphisms (SNPs) at the corticotrophin releasing hormone receptor 1 locus (CRHR1) in 460 women. Participants completed self-report questionnaires assessing symptoms of depression [Centers for Epidemiological Studies Depression Scale (CESD)], anxiety [State-Trait Anxiety Inventory (STAI) and Social Phobia and Anxiety Inventory (SPAI)], and mood [Positive and Negative Affect Schedule (PANAS)]. Results indicate a statistically significant interaction between CRHR1 genotype and the status of raising a child with FXS to predict social anxiety symptoms reported on the SPAI (rs7209436, P = 0.0001). Our data suggest that genetic variants in CRHR1 that associate with differential cortisol activation may also modulate levels of anxiety related to the stress of raising a child with FXS among women who carry an FMR1 premutation. © 2012 Wiley Periodicals, Inc.