Abstract: Globally, suicide is universally among the top twenty leading causes of death. Suicide risk, referring to the probability of occurrence of suicide attempts, has been widely studied, yet still lacks a reliable explanation as to the mechanisms of the suicide risk and its effective intervention. In the present article, we focus on a phenomenon that is both prevalent, culturally distinct, and challenging to the existing theories of suicide: In most countries in the world, males have a higher suicide rate than females; however, the sex ratio of the suicide of the Chinese population is markedly different and sometimes even reversed, meaning the male/female suicide ratio is less than one. Extant popular theories of suicide, such as the diathesis-stress model (Zubin & Spring, 1977), social integration and regulation theory (Durkheim, 2005), and interpersonal theory of suicide (Joiner, 2005; van Orden et al., 2010) do not provide ready explanations of this phenomenon. The present discussion aims to sort out the psychological theories and risk factors related to suicidal behavior, focusing on identifying risk factors and possible mechanisms that may contribute to sex differences in suicide.
Most previous explanations of the sex ratio of suicide held the following two viewpoints: (1) Males were more aggressive, more success-orientated, and more risk-taking with a higher rate of injury-producing behaviors than females, resulting in more males choosing lethal suicide methods, resulting in a higher suicide rate than females; (2) Cultural and social norms allow females to engage more in help-seeking behaviors but discourage males from showing their soft sides. In addition, suicide is reviewed more as a masculine behavior. Considering the challenging Chinese sex ratio of suicide rates, a recent theory of suicide has proposed four psychological strains as causes of suicide: conflicting values, conflicts between desires and realities, relative deprivation, and poor coping skills in the face of a life crisis.
In an attempt to search for psychological mechanisms of suicide in general and of the sex ratio in suicide risk in particular, we identified, from previous theories and research findings, two possible pathways leading to sex-specific suicide risks: (1) the number and quality of coping methods males and females use differentially to deal with psychological stress, and (2) cultural-specific social expectations for stress coping. The number of methods and socially available means for coping psychological stress may vary for males and females. For instance, men in China may have more effective social means to copy with psychological stress than women. In addition, social expectations regarding ability to cope with and tolerance to stressful events may also differ depending on the sex of the respondent. If men expect women to be more resilient to stressful events in life more than women actually do, such sex-specific expectancy may aggravate the stressful experience of women, reducing their chance of being helped and increasing their risk of suicide. From the perspective of domain-specific risk-taking, suicide risk is a unique domain of risk that is sensitive to life-history factors such as age, sex, birth order, and childhood family experience. Based on the predictions derived from life-history theory, we suggested several directions for future research to understand the sex ratio of suicide risk and to identify sex-specific and effective intervention strategies.

Key words: suicide risk, theories of suicide, the sex ratio of the suicide rate, life history, coping strategies of psychological stress, social expectancy