Suicide is a major health issue bringing its own specific challenges to the search for preventive strategies (“WHO | Suicide data,” n.d.). Suicide risk is associated with several psychiatric disorders including mood disorders. In line with this, the risk of suicide in patients presenting major depressive disorder (MDD) was found to be 25 times greater than that observed in the general population (Lépine and Briley, 2011; Tondo et al., 2007).

As well as psychiatric diagnosis, personal traits play a crucial role in determining suicide vulnerability. Impulsivity, which is associated with swift, unplanned cognitive and behavioural responses with no awareness of negative medium- and long-term consequences (Moeller et al., 2001), has been investigated as a major risk factor for suicide in particular. However, the relationship between suicide and impulsivity remains complex. A meta-analysis conducted by Anestis et al. found a significant association between these two clinical entities despite a weak correlation (Anestis et al., 2014a). Impulsivity may therefore be considered more as an indirect, distal risk for suicide as set out in Mann's diathesis model (Turecki et al., 2019). Impulsivity dimensions also differ, as suggested in another meta-analysis showing that the impact of the cognitive impulsivity dimension is greater in terms of suicide risk than behaviour regulation (Liu et al., 2017). Moreover, the impact of impulsivity could be modulated by other factors involving a longitudinal course and life events, i.e., it could be suggested that highly impulsive individuals are more likely to encounter traumatic and negative events that will in turn increase suicide risk (Anestis et al., 2014a). Conversely, impulsivity may well result from adverse child experiences, thus mediating the relationship between traumatic events in childhood and increased suicide risk (Turecki and Brent, 2016; Wanner et al., 2012).

Inconsistent definitions and therefore impulsivity assessments could explain these inconsistent findings. Impulsivity is a multidimensional construct (Beach et al., 2022). Different personality models could exacerbate the various components of impulsivity, resulting in heterogeneous assessments of impulsivity. While some theorists conceptualise impulsivity as primarily sensation-seeking (Cloninger et al., 1991), others have conceptualised it within other personality domains, such as extraversion and psychoticism (Eysenck and Eysenck, MW, n.d.). Wallace et al. have conceptualised impulsivity through a physiological perspective with distinct impulsive response pathways. Finally, impulsivity often combines trait-based impulsivity and state-based impulsivity (Wallace et al., 1991). However, these two components of impulsivity are assessed differently and are indicative of different processes (Lockwood et al., 2017). Therefore, it is difficult to draw conclusions regarding the role of impulsivity. Firstly, Barrat et al. concluded that there are three main sub-traits of impulsiveness: motor, cognitive and non-planning (Barratt, 1985). Secondly, Whiteside and Lynam (2001) conceptualised impulsivity through the Five-Factor Model of Personality (Whiteside and Lynam, 2001). Their original Impulsivity Scale model consists of four sub-scales: Negative Urgency, (lack of) Premeditation, (lack of) Perseverance and Sensation-Seeking. A fifth factor, positive urgency, has been added to the model, which refers to impulsive actions in response to positive affect (Cyders et al., 2007). Negative urgency refers to impulsive actions in response to negative affect. Positive urgency refers to impulsive actions in response to positive affect. Lack of premeditation measures refers to the extent to which one acts without considering the consequences of such action. Lack of perseverance assesses one's inability to sustain attention. Sensation-seeking refers to the pursuit of exciting activities and openness to experiences (Beach et al., 2022; Cyders et al., 2007; Whiteside and Lynam, 2001).

A link between impulsivity and suicide risk was observed in a depressed population (Oquendo et al., 2004; Perroud et al., 2011). However, the link between impulsivity and suicide attempts is inconsistent (Henna et al., 2013; Keilp et al., 2006). This may be due to clinical severity (Corruble et al., 2003; Hur and Kim, 2009). In addition, suicide attempts in severe depression were postulated to be related preferentially to loss of control and cognitive impulsivity (Corruble et al., 2003). However, increased impulsivity was also reported in MDD patients in euthymic phases (Henna et al., 2013; Ozten and Erol, 2019; Saddichha and Schuetz, 2014), suggesting that impulsivity could well be a personality trait regardless of the stage of illness.

Other clinical factors such as self-esteem (Brausch and Decker, 2014; Mitsui et al., 2014) or anxiety (Fava et al., 2004; Saade et al., 2019) may influence suicidal ideation and behaviour in MDD patients. Indeed, in a recent machine-learning study, the authors highlighted that suicidal thoughts, trait anxiety, depressive symptoms and self-esteem were the four highest predictors of suicidal behaviours in a student population (Macalli et al., 2021). Self-esteem is known to be an important marker of psychological vulnerability in young adults (Arsandaux et al., 2021) and is linked to suicidality (Harpin et al., 2016). Moreover, in the general population, some personality traits such as negative affect and low-self-esteem were associated with increased suicide risk (Turecki et al., 2019).

In addition, it is now well established that anxiety could increase the risk of suicide in a depressed population. This association was identified in both young adults (Moller et al., 2022) and older individuals (Fernandez-Rodrigues et al., 2022). Among the key factors that mediate between distal risk factors (i.e., familial and genetic predispositions, early life adversity, etc.) and proximal factors (i.e., life events, psychopathology, substance abuse, etc.), anxiety and impulsive-aggressive traits were strongly associated with suicidal behaviours (Turecki et al., 2019). However, anxiety appears to be a contributing factor in suicide attempts where it interacts with other factors in vulnerable individuals who are already more prone to suicide (Turecki et al., 2019).

Among MDD subjects, one-third will experience treatment resistance defined by the failure of two or more adequate trials (Berlim and Turecki, 2007; Ruhé et al., 2012; Kautzky et al., 2019; Rush et al., 2006; Souery et al., 2007). In addition, approximately 30 % of this population of treatment-resistant depressed (TRD) patients will have attempted suicide at some point in their lives (Bergfeld et al., 2018; Hantouche et al., 2010). Moreover, suicide risk is also considered a risk factor for treatment failure (Bennabi et al., 2015; Lopez-Castroman et al., 2016). However, to date, no published study has investigated the relationship between impulsivity and suicide in TRD. On this basis, we propose to review the relationship between impulsivity and suicide risk in a cohort of French patients presenting TRD and to study the potential impact of some clinical features such as anxiety, self-esteem and childhood trauma.