The association between oestrogen, memory, cognition and mood in a male-to-female transsexual population
Research has demonstrated that gonadal hormones, including oestrogen, can influence memory and cognitive tasks that show sex differences in animals and humans. Beneficial effects of oestrogen on mood have also been reported in postmenopausal women in association with Oestrogen Replacement Therapy (ERT). Male-to-Female (M-F) transsexuals offer one of the few opportunities for studying the effect of oestrogen and other cross-sex hormones on human cognitive function. The present research examined the effect of gonadal hormones on memory, cognition and mood in a transsexual population. The aim was to determine whether treatment with oestrogen and other cross-sex hormones would influence memory and cognitive abilities that show sex differences, such that males treated with oestrogen and other cross-sex hormones would perform more like females. We also examined the effect of such hormone treatment on mood. In an initial study (Chapter 2), M-F transsexuals undergoing oestrogen treatment for sex re-assignment scored higher on Verbal Paired Associate Learning (PAL) compared to a similar transsexual control group, awaiting oestrogen treatment. No differences between these groups were detected on a control memory task (Digit Span) or on other cognitive tasks that show sex differences, including Mental Rotations and Controlled Associations. In a second study (Chapter 3), an attempt was made to summarise the magnitude and reliability of sex differences in some of the memory tasks previously used in oestrogen and memory research. In a final study (Chapter 4), a more robust design was used to further examine the association between oestrogen, memory, cognition and mood. Additional aspects of memory function and other cognitive abilities that do and do not show sex differences were used, including verbal and visual-spatial abilities. Also, a repeated measures design was used. M-F transsexuals were tested both prior to hormone treatment and after treatment had begun. In addition, some M-F transsexuals were tested both before and during a period of hormone withdrawal prior to surgery. Findings from this study did not replicate the data from the initial study reported in Chapter 2. Few changes in memory or other aspects of cognitive performance were observed and these were not consistent in the two groups of patients. Improvements in mood were observed, particularly at the commencement of oestrogen treatment. However, this improvement could have resulted from progression in the treatment program rather than from the hormone treatment per se.