The differences in suicidal behavior by gender have been revealed by many studies, for example, women attempt suicide at a higher rate than men, but men are the ones who eventually die more often from suicide. In order to prevent possible suicidal behavior, one should conduct more studies on people who attempt suicide, because people who attempt suicide may also reappear in the future, but there are very few relevant studies on gender differences in suicidal populations. Therefore, the results of a two-year follow-up of 314 patients with major depressive disorder or bipolar disorder showed that different warning factors for suicidal behavior had different effects by gender. 1. Early warning factors in the male population Some studies have found that substance abuse is a possible risk factor for suicide. However, in the current study, substance abuse was only predictive of suicidal behavior in men, and this result is consistent with many clinical facts. For men experiencing problems in important interpersonal relationships, drug and alcohol abuse can add risk to suicidal behavior. Researchers have suggested that aggression and hostility may be important factors in male suicide, and the data support a role for both in male suicide, but this role does not reach significant levels, meaning that the predictive role of aggression and hostility for suicide is not statistically clear. However, in the current study, anger was found to be a predictor of suicidal ideation in young men. So, the effect of anger as well as aggression on suicide is actually quite complex. In the study, family history of suicide was only predictive of future suicide in male patients, yet there are other studies that show the opposite result. The effect of family history of suicide on future suicides can be explained by a genetic perspective, but the way in which genes affect different genders is not clear and needs to be further elaborated in future studies. For males, parental separation at a young age increases the likelihood of suicide more than twofold. The loss of a father or mother at a young age is also an important factor influencing suicide, and this has implications for females as well. 2. Early warning factors in the female population In the female population, depression, reduced survival reasons, and borderline personality disorder are all direct predictors of suicidal behavior. In terms of depressed mood, the data show that every point increase in women on the Beck Depression Inventory increases the risk of suicide by 4%. The effect of depression on suicide was found for women of all ages, but depression was found only for older men. For survival reasons, the researchers tested people on the Reasons for Survival Scale and showed that being married was protective for men, while having children was protective for women. That is, married men and women with children would perceive a greater responsibility and obligation to survive, and these reasons for surviving could somewhat prevent people from taking the path to suicide. In addition, factors that may increase a woman’s risk of suicide include having a history of suicide attempts, suicidal ideation, lethality of prior suicidal behavior, and hostility. Prior suicidal behavior can increase the risk of suicide again by 30%. For suicidal ideation, some studies have shown that it has a greater impact on younger women. However, the link between suicidal ideation and suicidal behavior has not been established. In addition, increased hostility can lead to an increased risk of suicide. Hostility and depression are interrelated and can be predictive of suicidal behavior, but the mechanism behind this predictive effect is unclear. 3. Early warning factors that jointly affect men and women Borderline personality increases the risk of suicide in women, but in fact this factor also increases the risk of suicide in depressed men. Whether male or female, if a person suffers from both major depressive disorder and borderline personality disorder, he or she is more likely to attempt and commit suicide than someone who suffers from only one of these disorders. In addition to this there is another factor that is predictive of suicidal behavior in both men and women, and that is smoking behavior. Smoking can act independently of the effects of depression and alcohol abuse to increase the risk of suicide, while smokers are also perceived to be more aggressive and to have more impulsive behaviors. In summary, different factors have different predictive effects on suicide in depressed men and women, and some factors can act on both male and female populations. Knowledge of gender-specific risk factors for suicide may not only help health care providers to improve their evaluation criteria, but also help people to better understand and help themselves.