Sex differences in PTSD are well-established with a 2:1 sex ratio favouring women. Less well-established is the basis of such differences. The purpose of this review is to explore recent research examining potential gender- and sex-based contributors to sex differences in PTSD.We identified 19 studies published since 2015. Masculinity is inconclusively associated with PTSD, but masculine ideals and masculine gender role stress are positively associated with PTSD. Among the sex-related factors, testosterone, oestradiol, progesterone, and ALLO/5α-progesterone ratio are believed to be involved in the development of PTSD. These factors likely affect PTSD risk directly and through epigenetic mechanisms. Findings suggest that gender and sex have multiple ways of affecting PTSD, including gender roles, genetic predisposition, and hormonal influences. These factors work together to put women at a particular risk of developing PTSD. By conducting more research, we may improve prediction, prevention, and treatment of PTSD.