Hormonal intrauterine device use is related to mental rotations but not verbal memory skills

There is perennial public and scientific interest in the neuroendocrine mechanisms underlying the large gender difference in three-dimensional (3D) mental rotation skills (favoring men) and small-to-moderate difference in verbal memory (favoring women). Past research has linked androgenic progestins in oral contraceptives to enhanced spatial skills, particularly 3D mental rotations, and estradiol to enhanced verbal memory skills. Hormonal intrauterine devices (IUDs) contain an androgenic progestin (i.e., levonorgestrel) without synthetic estradiol, but there is little-to-no systematic research on the cognitive impacts of use. The current study filled this knowledge gap in a sample of 343 participants (M_age = 21.75, SD = 4.52; 57.0 % White; 84.8 % non-Latine), comparing 50 hormonal IUD users to 135 naturally cycling (NC) females who were not menstruating and to 158 males. Compared to NC females, IUD users had better 3D mental rotation performance, but similar verbal memory. Compared to males, IUD users had similar 3D mental rotations performance, but better verbal memory. Group differences were generally moderate in size, and the pattern of results persisted when both age and general cognitive ability were covaried. Findings in IUD users are consistent with hypotheses, evidencing a potential and selective impact of exogenous androgenic progestin exposure on spatial cognition, and no effects on verbal memory, as expected given the preservation of endogenous ovarian hormone function that is not suppressed as it is in other hormonal contraceptives (e.g., oral).