Identifying differences between depressed adolescent suicide ideators and attempters

Highlights

• Suicide is the second leading cause of death among adolescents.

• Adolescent suicide attempters are characterized by greater anhedonia severity.

• Depressed suicide attempters do not integrate rewarding experiences.

Abstract

Background

Adolescent depression and suicide are pressing public health concerns, and identifying key differences among suicide ideators and attempters is critical. The goal of the current study is to test whether depressed adolescent suicide attempters report greater anhedonia severity and exhibit aberrant effort–cost computations in the face of uncertainty.

Methods

Depressed adolescents (n=101) ages 13–19 years were administered structured clinical interviews to assess current mental health disorders and a history of suicidality (suicide ideators=55, suicide attempters=46). Then, participants completed self-report instruments assessing symptoms of suicidal ideation, depression, anhedonia, and anxiety as well as a computerized effort–cost computation task.

Results

Compared with depressed adolescent suicide ideators, attempters report greater anhedonia severity, even after concurrently controlling for symptoms of suicidal ideation, depression, and anxiety. Additionally, when completing the effort–cost computation task, suicide attempters are less likely to pursue the difficult, high value option when outcomes are uncertain. Follow-up, trial-level analyses of effort–cost computations suggest that receipt of reward does not influence future decision-making among suicide attempters, however, suicide ideators exhibit a win–stay approach when receiving rewards on previous trials.

Limitations

Findings should be considered in light of limitations including a modest sample size, which limits generalizability, and the cross-sectional design.

Conclusions

Depressed adolescent suicide attempters are characterized by greater anhedonia severity, which may impair the ability to integrate previous rewarding experiences to inform future decisions. Taken together, this may generate a feeling of powerlessness that contributes to increased suicidality and a needless loss of life.

Introduction

Adolescent depression and suicide are serious public health concerns. The lifetime prevalence of depression in adolescence is 11% (Avenevoli et al., 2015), and depressive episodes are associated with poor psychosocial functioning (e.g., greater discord with parents, lower academic performance), more frequent engagement in risky behaviors (e.g., substance use, precocious sexual behaviors), and suicidality (Auerbach et al., 2010, Frojd et al., 2008). Presently, suicide is the second leading cause of death among youth ages 13–18 (Centers for Disease Control and Prevention, 2013), and depressed adolescents have a 6-fold greater likelihood of making a suicide attempt (Nock et al., 2013). Nevertheless, the explicit link between depression and suicidality remains unclear. For adolescents, depression is among the strongest predictors of suicidal ideation and plans but shows a weaker relationship with suicide attempts, and critically, only a third of adolescent ideators make an attempt (Nock et al., 2013). However, few prior studies have examined potential mechanisms that can explain how depression contributes to the transition from ideation to attempt.

Both depression and suicide are characterized by diminished motivation and deficits in reward processing (Auerbach et al., 2014a, Dombrovski et al., 2013). In animal studies, dysfunction within the mesocorticolimbic pathway contributes to reduced social drive and reward pursuit, which has been depicted as a depression-like behavior (Mintz et al., 2005, Strekalova et al., 2004). Among humans, anhedonia – a reduced ability to experience pleasure – is a core feature in depression (Pizzagalli et al., 2005), and both depressed adolescents (Boger et al., 2014, Forbes et al., 2009) and adults (Bogdan and Pizzagalli, 2006, Pizzagalli et al., 2008) exhibit reward dysfunction, which may be a promising phenotype of depression. Converging evidence from neuroimaging studies characterizing the neuropathology of these reward deficits has highlighted dysfunction within the anterior cingulate cortex (Steele et al., 2007) and striatum (Pizzagalli et al., 2009). Less research has examined behavioral and neural correlates of anhedonia in suicide, although studies have revealed that suicide attempters show aberrant reward signaling (Dombrovski et al., 2013) and abnormal striatum structure (Ahearn et al., 2001, Vang et al., 2010), compared with non-suicidal individuals.

Indeed, anhedonia may be a promising predictor of suicidal behavior, as it has long been theorized that suicide is a decision to escape from intolerable conditions when there is no expectation of relief (Baumeister, 1990, Hawton et al., 1982, Nock and Kazdin, 2002). Along these lines, Nock and Kazdin (2002) posit that for many, the experience of anhedonia is insufferable, especially because it tends to be chronic and stable over time (Clark et al., 1984). Although there seem to be clear theoretical connections between anhedonia and suicidal behaviors, results have been equivocal. In adults, anhedonia predicted suicide completions in severe psychiatric patients within 1 year of assessment (Fawcett et al., 1990). These findings were largely replicated in an independent sample: anhedonia was present in early (i.e., 1 year of the assessment) but not late (after 1 year of the assessment) suicide completions (Coryell and Young, 2005). Other research, however, found that anhedonia did not prospectively predict suicide attempts. Rather, there was a stronger relationship between low anhedonia and increased likelihood of suicidal behaviors, and the researchers suggested that the presence of high energy and elevated emotion might be a necessary condition for suicidality (Loas, 2007, Watson and Kucala, 1978).

Comparatively less research, however, has been conducted in youth. In a study of children ages 6–13 admitted to an acute psychiatric facility, anhedonia was associated with the presence of a suicide attempt even after controlling for depressed mood. Moreover, greater anhedonia severity distinguished psychiatric inpatient suicide attempters and ideators (Nock and Kazdin, 2002). Similarly, in a study of adolescents, higher levels of anhedonia distinguished youth reporting a history of both suicide attempts and nonsuicidal self-injury from those with no suicide attempt history and current nonsuicidal self-injury (Brausch and Gutierrez, 2010). Yet, the study did not account for the potential influence of current depressive symptoms or suicidal ideation, which makes it challenging to ascertain the unique effect of anhedonia on suicide attempt status. By contrast, another adolescent study found that greater anhedonia was correlated with suicidal ideation but not intent (i.e., suicide plan); the study did not assess the occurrence of suicide attempts (Chabrol et al., 2007). Although this research is a promising start to parsing the effect of anhedonia on suicide attempts in youth, important gaps remain, particularly in understanding how anhedonia may contribute to suicide attempts among depressed adolescents.

Anhedonia impairs the ability to integrate rewarding experiences (Pizzagalli et al., 2005), which is essential for informing future decisions, and consequently, this might be one path that leads to attempting suicide. Specifically, as anhedonia is characterized by marked diminishment in pleasure in previously enjoyed activities (Pizzagalli et al., 2008), these experiences are not viewed as positive, and therefore, they are unlikely to increase the likelihood of engaging in them in the future. A possible downstream consequence is that anhedonic individuals tend to make abnormal effort–cost computations. Meaning, they avoid previously enjoyed activities as they overestimate the cost (i.e., effort expenditure) and underestimate the benefit (i.e., future reward) (Gold et al., 2012, Gold et al., 2013) – especially when the perceived benefit is uncertain – which reduces engagement in pursuing rewards across social (e.g., spending time with friends) and experiential (e.g., playing sports) domains. Over time, this decreases the opportunity to experience pleasure, which may contribute to the chronicity of anhedonia and increased suicidality.

The goal of the current study is to test whether depressed adolescent suicide attempters show increased anhedonic behaviors compared with ideators that have comparable symptom severity across depression, anxiety, and suicidal ideation. As the two groups do not differ on key clinical variables, any resulting differences cannot be attributed to symptom severity. We tested the following a priori hypotheses. First, we hypothesized that relative to ideators, suicide attempters would report greater levels of anhedonia even after controlling for current symptom severity. Second, for individuals experiencing anhedonia, the value of future rewards may not offer sufficient motivation to pursue goal-directed behaviors, particularly when: (a) the reward is uncertain and (b) the costs (i.e., effort expenditure) to obtain the rewards are perceived as outweighing the benefits (Gold et al., 2013). This abnormal effort–cost computation may be more pronounced in suicide attempters reporting more severe anhedonia, and thus, we hypothesized that compared to suicide ideators, attempters will be less likely to pursue uncertain, but not certain, rewards. Last, using a fine-grained approach to examine the effort–cost computation deficit, trial-level data analysis will demonstrate that suicide ideators and attempters differ in their behavior following receipt of rewards. Specifically, we hypothesize that for suicide attempters, reward receipt will not influence the pursuit of future rewards. By contrast, suicide ideators will be more likely to exhibit a win–stay approach – repeat the selection of an option after receiving a reward.