Suicidal ideation mechanism is the psychological process of how thoughts of killing oneself emerge and persist in the mind. From the mindsponge-based Mindsponge-based suicidal ideation mechanism perspective, there are two conditions for suicidal ideation to happen: (1) the existence of accessible suicide-related information in the environment, and (2) the subjective perception that suicide being a beneficial option. Psychosocial factors (e.g. social connectedness or burdensomeness) can affect these two conditions and, in turn, influence the probability of suicidal ideation.
Suicidal ideation is thinking about self-killing; in other words, suicidal ideation is the formation of suicidal thought(s) within one’s mind. However, currently, in the scientific community, there is no consensus on the definition of suicidal ideation. Some definitions also include suicide planning while others do not. This lack of a universal definition cause difficulties in comparing findings across related studies . Suicidal ideation can be considered a prerequisite condition for deliberate suicidal actions to be carried out (including planning and attempting). Although suicidal ideation alone in itself is non-fatal, it increases the risk of suicidal attempts . However, the association between suicidal ideation and a suicidal attempt is still debatable. Recent developments in suicidal behavior studies have shown the distinction between the formation of suicidal thoughts and the progression into suicide attempts as well as the distinction between predictors of each phenomenon .
Researchers have been trying to look for psychosocial risk factors of suicidal ideation (characteristics of a suicidal mind). In other words, they try to find the reasons why suicidal thoughts happen and establish the associations between those factors and suicidal ideation.
While inquiries about the causes of suicide have always existed throughout human history, the early approaches presented here are in the context of modern scientific methodologies .
Some early major works in the 19th century include The Lawful Regularity of Apparently Voluntary Human Actions Seen from the Standpoint of Statistics (Adolf Heinrich Gotthilf Wagner, 1864) , Suicide: An Essay on Comparative Moral Statistics (Enrico Morselli, 1887) , and the reviews of suicide research by Daniel Hack Tuke in 1892 . These early studies share the approach in which the statistics of suicide can be directly inferred to provide understanding about the phenomenon of suicide. They look for the patterns of suicidal acts within the statistics of suicide, such as statistical irregularities found in certain situations. For example, climatic conditions and seasonal temperatures are investigated as the risk factors for suicide.
In 1897, the book Suicide: A study in sociology by Émile Durkheim  was published and later considered as the foundation for modern suicidology. Durkheim emphasized the role of psychosocial factors in suicidality and categorized suicide into four types: egoistic, altruistic, anomic, and fatalistic. Egoistic and altruistic suicides belong to the aspect of social integration (low and high level respectively) with major factors such as social connectedness and interconnectedness. Anomic and fatalistic suicides belong to the aspect of social regulation (low and high level respectively) with major factors such as anarchy and social oppression. In such cases, suicide attempts are the expression of reaching an extreme level in the spectrum of social integration or regulation.
Several major theories regarding suicide in modern times are listed below together with a summary of their main principles related to suicidal ideation.
To explore deeper into the “how” aspect of suicidal ideation and develop a framework that is consistent with former widely supported theories and findings, Nguyen et al. propose the suicidal ideation mechanism  based on the Mindsponge theory of information processing .
According to this mechanism, there are two fundamental conditions for suicidal thoughts to emerge and persist within the mind: (1) suicide-related information needs to exist in the surrounding environment and (2) the value of suicide needs to be perceived as “beneficial” (in other words the suicide-related information must be accepted by the current mindset). It is important to note that this acceptance varies in belief strength. The acceptance is temporary or partial at a low level of suicide desire. If the value of suicide is reinforced enough and become deeply integrated into the mindset, the decision to carry out the corresponding behavior (suicide attempt) may occur.
As one of the main principles of the Mindsponge framework states that a value is accepted when its perceived benefit is greater than its perceived cost, in the context of suicidality, a person accepting the value of suicide into their mindset when he/she perceives suicide to have more benefit over its cost. The perceived costs of suicide are the negative values attached to the act of suicide (e.g. biological death, impacts on social connections, the moral implication of self-killing, etc.). The perceived benefit of suicide is the cessation of suffering attached to the current and projected future state of living (e.g. physical or psychological pain, etc.).
In this information processing mechanism, the sense of connectedness can act as a trust factor (“priority pass”) in the filtering process. A higher level of connectedness means easier reception and acceptance of information from other people in society. It is worth noting that depending on the information sources and contexts, this effect can be either positive (e.g. in cases of help-related information ) or negative (e.g. in cases of suicide contagion ). Similarly, other psychosocial factors can influence the probability of suicidal ideation by affecting the information accessibility of information supporting or negating suicide desire as well as affecting the cost-benefit-based filtering processes of such information. For example, the psycho-religious mechanism of suicide was developed based on the same principles with the interactions with religiosity .