Changes in affect variability after starting gender-affirming hormone therapy

Affect variability is determined by how often and how strongly negative affect changes over time. Cisgender women report greater variability in affect than cisgender men. It has been suggested that sex hormone changes may influence affect variability. Transgender people frequently opt to use sex hormones in the form of gender-affirming hormone therapy (GAHT), but the extent to which GAHT can change negative affect variability is not yet clear. Therefore, this study aims to study changes in negative affect variability after starting GAHT. We have included data from 94 participants from the RESTED study: 49 transmasculine (TM) participants (assigned female at birth, starting testosterone) and 45 transfeminine (TF) participants (assigned male at birth, starting estrogens and anti-androgens). Participants completed up to 7 consecutive daily diaries at each of three time points: before starting GAHT, and after 3 and 12 months of GAHT. The daily diaries collected participants' reports on symptoms related to negative affect: experienced low mood, less interest, tense feelings and restless feelings. We have used linear mixed models to compare negative affect variability during one week, corrected for mean negative affect, between gender groups (TM versus TF) and measurement time points. Results show that in the TM group, variability in low mood, tense feelings and restless feelings decreases after 12 months of GAHT. In the TF group, variability in low mood increases after 3 months and 12 months of GAHT, as does variability in restless feelings after 3 months of GAHT. Group comparisons indicate significant group differences in changes in variability in low mood and restless feelings, with stronger increases in variability of negative affect in the TF group compared to TM group after 3 and 12 months of GAHT. Our findings indicate that variability patterns in negative affect in transgender persons tend to cross-over from being consistent with sex assigned at birth before GAHT to being more in line with gender identity after 12 months of GAHT. Future studies should focus on measuring both negative and positive affect variability during GAHT, preferably through multiple measurements per day, taking into account diverse social and daily contextual factors during GAHT.