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Description
Over 150 million women use hormonal intrauterine devices (IUDs) that prevent pregnancy by releasing a constant dose of the androgenic progestin levonorgestrel into uterine tissue. Past research has linked androgenic progestins to enhanced spatial skills, particularly three-dimensional (3D) mental rotations; yet there is no systematic research on spatial skills in IUD users. The current study filled this knowledge gap, comparing IUD users to oral contraceptive users and naturally cycling women. IUD users were hypothesized to outperform other groups due to their continuous levonorgestrel exposure.
Data collection is ongoing, with 184 participants (M age =21.86, SD=4.72; 74.5% White; 84.2% non-Latina) having no gynecological problems or hormonal medication intake and using the same hormonal contraceptive–or not–for ≥3 months: 48 hormonal IUD users, 41 naturally women not menstruating, and 95 oral contraceptive users on active pill.
Participants came from a Midwest university and surrounding community. They completed laboratory-based testing of their spatial skills using the 20-item Vandenburg and Kuse 3D Mental Rotation Task. A point was received for an item when 2 of 4 accurate rotations of the 3D target image (shown in 2D space) were identified.
One-way analyses of (co)variance were used to examine group differences in performance, with Tukey-LSD follow-ups; sensitivity analyses controlled for age and general cognitive ability (indexed by vocabulary). As expected, IUD users (M=12.10, SD=4.73) had better mental rotations performance than naturally cycling women (M=9.59, SD=5.31), p=.018, d=0.51, but not oral contraceptive users (M=10.65, SD=4.87), p=.099, d=0.30. Differences between IUD users and naturally cycling women persisted, with reductions in effect size, when age (d=0.50) and general cognitive ability were controlled (d=0.31).
Findings are consistent with the notion that high androgenic activity of progestins in IUDs promotes spatial skills. Future work will unpack the heterogeneity of oral contraceptive formulations (e.g., androgenic activity) in a larger sample.
