Covariates.

Covariates were chosen based on extant literature suggesting possible associations. Specifically, the following variables were considered as covariates: child sex assigned at birth (hereafter, child sex), gestational age at birth, maternal education, and smoking during pregnancy (Mileva-Seitz et al., 2015; Suor et al., 2017). Child sex was based on maternal report. Gestational age, extracted from birth records, was considered as a continuous variable. Maternal education was scored as less than high school diploma, high-school diploma/GED, some college, college degree, or graduate degree, based on maternal report. Maternal smoking during pregnancy was categorized as yes/no based on maternal self-report of smoking at recruitment and/or in the third trimester, a validated method for classifying prenatal smoking status (Pickett, Kasza, Biesecker, Wright, & Wakschlag, 2009). In secondary analyses, sex was considered as a moderating variable, as described below. Post hoc analyses tested for effects of maternal age (measured continuously); pregnancy complications (gestational diabetes or pre-/eclampsia, measured as dichotomous yes/no variable); parity (measured continuously as number of older children); maternal exposure to negative life events in the past year (measured continuously, using the CRISYS-R [Berry, Quinn, Shalowitz, & Wolf, 2001], when children were 3.5 years of age), and maternal mental health symptoms, measured when children were 3.5 years of age (concurrent with BRIEF-P ratings): anxiety (measured continuously with the Trait subscale of the STAI; Spielberger, Gorsuch, & Lushene, 1970), depression (measured continuously with the EPDS; Cox, Holden, & Sagovsky, 1987), and PTSD (measured continuously, with the PCL-C; Weathers, Litz, Herman, Huska, & Keane, 1993).