Study participants

In 1986–1988, families of children attending nursery school in public francophone schools in Quebec, Canada, were recruited using a multistage sampling procedure. From 4488 participating children, two subsamples were selected for follow-up. The first was a randomly selected group of 1001 boys and 999 girls: the representative subsample (R). The second was an additional group of 593 boys and 424 girls, oversampled for children exhibiting disruptive behaviours: the disruptive subsample (D). To reduce cultural heterogeneity, only children whose parents were born in Canada and whose mother tongue was French were included; 88% were of non-Hispanic White ethnicity.

The assessment schedule had three stages:

1. (a) wave 1 (childhood), yearly assessments age 6–12 years; representative sample n=2000, disruptive sample n=1017;

2. (b) wave 2 (mid-adolescence), average age 15.7 years (range 15–18); representative sample n=1233, disruptive sample n=482;

3. (c) wave 3 (adulthood), average age 21.4 years (range 19–24); representative sample n=1144, disruptive sample n=540.

Participants who had died, refused participation or could not be contacted accounted for an overall attrition rate of 44% (R 43%, D 47%). To adjust for this, we conducted multivariate analyses with and without weights, representing individual probabilities of remaining in the study conditional on variables related to attrition: mean early socio-economic adversity, which was higher in non-responders (R 0.32 v. 0.25, t _(1,1893.5)=–7.410, P=0.0005; D 0.39 v. 0.32, t _(1,1893.5)=–2.161, P=0.031), and male gender, as males were overrepresented among non-responders (R 50% v. 35%, χ² ₁=46.05, P<0.05; D 55% v. 36%, χ² ₁=36.30, P<0.05). The study was approved by the research ethics boards of the University of Montreal and McGill University. Written informed consent was obtained from all participants.

Measures

Data analyses

Identification of correlates and moderators of suicide attempts

Our hypotheses regarding the correlates of suicide attempts focused on four domains. Because high social support buffers the impact of stress and guards against social isolation (two important triggers of suicidal behaviours), we expected social support and stressful life events ^{Reference Straus16} to represent significant correlates of suicide attempts. These expectations were not met in any of our abuse groups. Second, among socio-demographic factors, as expected, ^{Reference Beautrais3} female gender was associated with suicide attempts in the group who experienced both types of abuse, as was one of the four aspects of early socio-economic adversity (paternal education: physical-abuse group OR=0.71, 95% CI 0.58–0.88). In contrast to previous research, neither adult income nor the remaining three components of early socio-economic adversity were related to suicide attempts. ^{Reference Beautrais, Wells, McGee and Oakley Browne17,Reference King, Schwab-Stone, Flisher, Greenwald, Kramer, Goodman, Lahey, Shaffer and Gould18}

Our hypothesis that suicidal ideation ^{Reference O'Boyle and Brandon19} might be of relevance for suicide attempts was met in all three abuse groups (sexual abuse OR=6.7, 95% CI 2.6–17.2; physical abuse OR=5.8, 95% CI 2.9–11.7; both OR=4.5, 95% CI 2.1–9.6). In terms of psychiatric diagnoses, in contrast to previous research evidence, ^{Reference O'Boyle and Brandon19} we were unable to confirm the involvement of adolescent mood and anxiety disorders or adult substance misuse. ^{Reference Kessler, Borges and Walters20} The opposite was true for disruptive disorder, an important correlate of suicide attempts in our physical-abuse group (OR=3.1, 95% CI 1.1–9.1) (Table 2).

Table 2

Correlates of suicide attempts in participants reporting childhood physical abuse

	B (s.e.)	Exp[B] (95% CI)
Confounders
Disruptive sample membershipa	-0.54 (0.64)	0.58 (0.17-2.04)
Gender	0.34 (0.47)b	3.69 (0.95-14.39)
Regressors
Paternal education	-0.34 (0.11)**	0.71 (0.58-0.88)
Disruptive disorders	1.13 (0.55)*	3.10 (1.05-9.15)
Lifetime suicidal ideas	1.76 (0.35)***	5.84 (2.91-11.67)
Model indices	Model fit: χ2 5=50.99, P=0.0005
	Nagelkerke R 2=47.9%
	Hosmer—Lemeshow test: χ2 8=6.50, P=0.59

Fourth, we predicted significant contributions of several personality traits related to emotional dysregulation and impulsive-aggression, ^{Reference Brezo, Paris and Turecki4} given their involvement in essential aspects of functioning: self-perception (identity problems and self-esteem), ^{Reference Dinwiddie, Heath, Dunne, Bucholz, Madden, Slutske, Bierut, Statham and Martin21} interpretation (cognitive–perceptive dysregulation), interaction (submissiveness, disruptiveness, insecure attachment, social avoidance and suspiciousness) and reaction to social environments (passive-aggressivity, affective instability, anxiousness). Two of these traits – childhood aggression/disruptiveness (sexual-abuse group OR=1.4, 95% CI 1.1–1.8; both abuse types OR=4.6, 95% CI 1.1–18.2) and adolescent/adult conduct problems (both abuse types OR=1.1, 95% CI 1.01–1.2) – made significant contributions (Tables 3 and 4).

Table 3

Correlates of suicide attempts in participants reporting childhood sexual abuse^a

	B (s.e.)	Exp[B] (95% CI)
Confounders
Disruptive sample membershipb	1.01 (0.83)	2.73 (0.53-14.06)
Gender	-1.44 (1.11)	0.24 (0.03-2.09)
Regressors
Lifetime suicidal ideas	1.91 (0.48)***	6.74 (2.64-17.23)
Abuse frequency and abuser identity	1.21 (0.45)**	3.37 (1.40-8.13)
Aggressionc	0.34 (0.13)*	1.41 (1.08-1.83)
Model indices	Model fit: χ2 5=44.85, P=0.0005
	Nagelkerke R 2=57.9%
	Hosmer—Lemeshow test: χ2 8=2.32, P=0.97

Table 4

Correlates of suicide attempts in participants reporting both sexual and physical abuse in childhood^a

	B (s.e.)	Exp[B] (95% CI)
Confounders
Disruptive sample membershipb	1.52 (0.70)*	4.59 (1.15-18.23)
Gender	5.56 (1.76)**	259.2 (8.30-8093.01)
Regressors
Lifetime suicidal ideas	1.49 (0.39)***	4.45 (2.07-9.58)
Conduct problems	0.09 (0.04)*	1.09 (1.01-1.19)
Model indices	Model fit: χ2 4=54.24, P=0.0005
	Nagelkerke R 2=62.0%
	Hosmer—Lemeshow test: χ2 8=4.83, P=0.78

Evidence for gender-based moderation of the risk of suicide attempts and suicidal ideation, especially in people experiencing childhood physical abuse, has been offered before. ^{Reference Windle, Windle, Scheidt and Miller15,Reference D'Eramo, Prinstein, Freeman, Grapentine and Spirito22} In our study, however, gender did not act as a moderator of the relationship of suicidal ideation and suicide attempts in the physical-abuse group.

On the basis of previous research suggesting that severe childhood sexual abuse – that involving fathers or stepfathers, or repeated abuse – may be strongly associated with suicide attempts, ^{Reference Hebert, Parent, Daignault and Tourigny23} we also tested evidence of moderation by three sexual abuse characteristics: abuser identity, abuse frequency and abuse severity. Although none of the hypothetical moderating effects was significant, we did observe an interaction between abuse frequency and abuser identity (OR=3.4, 95% CI 1.4–8.1). Abuse frequency had a conditional effect on suicide attempts, and was, in turn, moderated by abuser identity. Repeated sexual abuse had a stronger association with suicide attempts than did onetime abuse (Fig. 1). Relative risk increased with the degree of relatedness between the child and the abuser: compared with participants reporting no history of childhood abuse, those abused by a non-related person (RR=2.3), a member of their extended family (RR=3.4) or a member of their immediate family (RR=5.0) had progressively higher likelihoods of reporting suicide attempts.

Distribution of suicidal behaviours

For the most part, participants with no history of childhood abuse had the lowest odds of non-fatal suicidal behaviours, and those reporting physical abuse, sexual abuse or both abuse types respectively had progressively higher odds of such behaviours. The existence of such a gradient has been suggested previously. ^{Reference Beitchman, Inglis and Schachter25} Stratification by gender further revealed that the gradient may be specific to female suicide attempters and ideators, corroborating evidence for gender-specific psychiatric consequences across abuse types. ^{Reference Thompson, Kingree and Desai26} This heterogeneity might be related to gender-specific gene–environment interactions, neurobiological changes, coping responses to childhood abuse and differential exposure levels to childhood trauma. ^{Reference Teicher, Andersen, Polcari, Navalta and Kim27}

Correlates and moderators of suicide attempts

Our primary hypothesis regarding Axis I disorders was supported only in adults reporting physical abuse in childhood. Satisfying criteria for attention-deficit hyperactivity disorder, conduct disorder and/or oppositional-defiant disorder tripled the likelihood of a positive suicide attempt history. Disruptive disorder symptoms, especially in those reporting physical abuse, have already been linked to suicidal behaviours. ^{Reference Renaud, Brent, Birmaher, Chiappetta and Bridge28} We were, however, unable to test if this association was mediated by substance use disorders, as previously suggested. ^{Reference Renaud, Brent, Birmaher, Chiappetta and Bridge28} This possibility seems unlikely in our sample, as substance misuse was not related to suicide attempts. Anxiety and mood disorders were similarly not significant, either because their contribution was limited to shared variance with suicidal ideation or because they are not important intermediaries between childhood abuse and suicide attempts.

Interestingly, we found that externalising personality traits assessed at different life stages may be of relevance to suicide attempts. Conduct problems – self-reported tendencies to engage in acts of vandalism or theft, alcohol intoxication, and bullying or threats of violence – contributed to the variance in suicide attempts in our group with both types of abuse. Furthermore, disruptive–aggressive personality traits in childhood were significant in both the combined-abuse group and the sexual-abuse group. These traits are related to impulsivity–aggression, a putative mediator of suicide risk. ^{Reference Turecki29} Similar traits have been implicated across age and gender groups. ^{Reference King, Schwab-Stone, Flisher, Greenwald, Kramer, Goodman, Lahey, Shaffer and Gould18}

Explanations for the involvement of externalising tendencies – impulsive–aggressive personality traits and disruptive disorders – are likely to involve interplays of abusive environments and genes. For example, externalising behaviour is predicted by high-intensity family conflict, a situation more likely to arise in abusive households. ^{Reference Hebert, Tremblay, Parent, Daignault and Piché30} Childhood abuse itself may influence the development of impulsivity and aggression, ^{Reference Brown, Cohen, Johnson and Smailes31} although its precise role is unknown. Our data demonstrated that aggression at age 6 years (our earliest personality measure) was most relevant, among those who had attempted suicide, in participants who reported the most severe childhood abuse type (both physical and sexual). Additionally, relative to sexually abused children, those experiencing both physical and sexual abuse were more likely to report abuse by family members rather than by unrelated persons, further supporting the notion of compound family adversity in abusive households. Ultimately, abuse in children may be not only involved in the aetiology of externalising tendencies but also a negative reinforcer of such tendencies through reactive gene–environment correlations: in other words, externalising behaviours may provoke negative reactions by adults and peers, leading to social difficulties, an important motivator of suicide attempts.

Unlike externalising tendencies, which exhibited some abuse specificity, suicidal thoughts made consistent contribution across abuse types in our study. Persistent suicidal ideation made suicide attempts 5–6 times more likely in those with a history of childhood abuse. Its relationship with suicide attempts was additive rather than moderated by gender and abuse characteristics, in contrast to our hypotheses. Suicidal thoughts, however, may be mediators between suicide attempts and maladaptive coping responses related to abuse.

Our exploration of the effect of childhood sexual abuse characteristics indicated that the impact of abuse frequency on suicide attempts depended on the identity of the abuser. Repeated abuse was, generally, more strongly associated with suicide attempts than was one-time abuse. Furthermore, sexual abuse by a member of the immediate family – father, stepfather or brother, for example – carried the greatest risk, whereas abuse perpetrated by an extended family member (uncle, cousin) or an unrelated individual (an acquaintance, romantic partner or stranger) carried intermediate and weaker risks respectively. There are at least two plausible explanations for this pattern. First, abuse by a father or stepfather is considered especially traumatic, ^{Reference D'Eramo, Prinstein, Freeman, Grapentine and Spirito22} possibly because such abuse is more likely to occur in families with multiple problems and also because these families cannot provide safe and healing conditions following abuse. Second, abuse by close family members, who are expected to be among our main, lifelong sources of support, may have long-term consequences on the development of healthy attachment patterns necessary for mental health. ^{Reference Allen and Farmer32}

Although we examined possible protective influences of adolescent self-esteem, social support, and childhood and adult environments, only paternal education was found to have such effect. Low parental education has already been recognised as a risk factor for childhood abuse. ^{Reference Straus16} We found it also to be strongly correlated with socio-economic status (r=0.58, P=0.0005), another factor positively related to mental health and exposure to abuse. ^{Reference Beitchman, Inglis and Schachter25} Better-educated parents might provide a more stable and healthy environment, one that would lower the likelihood of abuse taking place or reduce its impact. They might, furthermore, be less likely to use corporal punishment and similar disciplinary methods. When facing challenging situations themselves, educated parents might also model more adequate coping behaviours rather than resort to suicidal gestures and/or externalising behaviours.

In summary, the three abuse groups have both shared and distinct correlates of suicide attempts across diverse risk domains. Additional longitudinal studies need to examine childhood abuse in relation to the onset and developmental course of psychosocial problems, addressing moderating and mediating influences involving characteristics of abusive acts, the person abused, and the abuser.

Alternative methodological explanations of observed findings must also be noted. Our study population included self-reported abuse victims, excluding individuals who repressed memories of such events or chose not to report them. Nevertheless, we found those self-reporting abuse to be at higher risk of attempting suicide than those reporting no childhood abuse. Furthermore, not having information on the proportion of those who had received psychosocial interventions following abuse disclosure, we were unable to control for the possible confounding effects of such interventions. The lack of external validation of abusive experiences and attachment security, possibility of measurement error, and the small number of sexually abused male participants who had attempted suicide also merit consideration. We also note a modest departure from normality of the trait of conduct problems, although logistic regression is believed to be relatively robust to such departures.

To address the suboptimal psychometric properties of the suicidal ideation and intent scales – possibly attributable to translation problems – we used multiple instruments to assess suicidality. Still, more information is needed on the means used at self-injury. These limitations notwithstanding, our findings confirm the association between suicide attempts and childhood abuse, and involvement of both additive and interactive influences.