Each year more than 800,000 people die by suicide worldwide,1 representing 15% of the 15,000 fatal injuries occurring daily. In some countries, suicide is among the leading causes of death among the young; in fact, amongst those aged 15-29 years it is the second cause after road traffic injuries.1 Although Spain has one of the lowest suicide death rates in Europe, a total of 3,158 deaths were attributed to suicides in 2010.2 Furthermore suicide data could be underestimated as deaths or injuries may not be clearly identified as intentional. Suicidal behavior occurs along a continuum progressing from negative thoughts or ideations, plans, non-fatal suicide, and finally fatal suicide. Prevalence of suicidal ideations, thoughts and plans are more difficult to estimate than fatal suicides. Non-fatal suicidal behaviors are several times more frequent than fatal suicides (10, or more times) and they are among the most powerful predictors of subsequent suicide deaths.3 Prevalence of suicidal behaviors differs by sex: pessimistic thoughts and ideations are more frequent among women and men carry out more fatal suicides, rates being reported to be three times higher than in females.4

Suicidal behavior is a multifaceted problem for which presence of mental disorders increases risk.5 A majority of suicidal victims (more than 90%), have a diagnosable chronic mental disorder. The most prevalent psychiatric disorders in suicide deaths among the general population were depression, mood disorders, schizophrenia, and substance abuse.6 Previous studies have reported its association with substance use: one study found a five-fold increase in risk of suicide among alcohol abusers compared to social drinkers.7 Use of other psychoactive substances like heroin, cocaine and sedatives has also been linked to fatal suicides.8 The consumption of more than two substances has been linked to greater likelihood of both fatal and non-fatal suicidal behavior.9

Additionally, several studies have shown traumatic experiences were associated with greater suicide risk, developing thoughts of suicide and to plan attempts.5,10 The context of illegal drug use favours exposure to traumatic events.11,12 In fact, in the conceptual framework to explain the relationship between drug use and violence, one of the models introduced by Goldstein refers to systemic crime derived from illicit drug distribution and use.13 Ilgen's study went beyond the Goldstein model showing that illicit drug users in treatment with prior violent behaviour were more likely to report suicide attempts.14

The purpose of this study was to assess, separately by sex, the prevalence of suicidal ideations and plans among illicit drug users recruited in drug treatment facilities and its association with drug-scene contextual factors, including recent violent trauma experience and crime involvement.

A high prevalence of suicidal IP was observed among illicit drug users recruited in drug treatment facilities. Prevalence among women, although slightly higher didn’t differ statistically from that among men. Recent aggression, psychological treatment and previous illegal/marginal income generation activities were positively associated with suicidal IP for both men and women, while involvement in trafficking only among men and prison history was positively associated with suicidal IP among women and negatively among men.

Some limitations need to be considered when interpreting these results. First, this study provided evidence about the presence of ideations and plans during the previous 12 months, however it did not evaluate the frequency and intensity of them, or the presence of any non-fatal suicide attempt. Second, recruitment was done among illicit drug users in health centers, thus results can at most be representative of drug users in healthcare facilities. Third, being based on self-reported data, the results could be influenced by subjects tending to give answers considered “desirable”. In any case, if there was an under declaration of suicidal IP, reported prevalence would be an underestimate. Fourth, although the study sample is considerable, we cannot exclude a lack of statistical power, which would preclude finding some significant results; this would be especially important regarding a gender analysis perspective. In fact, it was not possible to analyze in depth the association of different forms of aggression with suicide behaviors due to small figures for some of them (e.g. sexual aggression). Fifth, not having assessed presence of mental disorders in our sample is a further limitation; although psychological treatment with the same reference period as suicidal IP was assessed and could be considered as a proxy of mental disorders it might also indicate a previous non-fatal suicide problem. Finally, being a cross-sectional design, we cannot draw conclusions about the directionality of the associations.

The study included analyses of suicide IP prevalence separately by sex, as factors associated with suicidal behaviors could differ for men and women. However, we haven’t been able to go deeper with a gender perspective as the study design didn’t consider all necessary aspects to this aim, like selective recruitment to achieve a larger sample of women or to better care for gender addressing questions (e.g. violence). Nevertheless, we can contribute to the gender debate by showing controversial results in men and women, like the differential outcome in subjects with a prison history or participation in drug trafficking. Also of note is the different direction for age, as in men the likelihood of suicidal IP increased with age, while for women it decreased.

Due to sample characteristics, substances used by subjects in the study were not considered in the multivariate analyses (e.g. 93% cocaine users may preclude finding an association with this substance). Furthermore, the sample included drug users in treatment, thus some of them might not be consuming in the period considered for assessing suicide (last 12 months) due to being in therapeutic communities or in substitution treatment. Besides, although alcohol was included in the analysis as its reporting was referring to the same period of time, it was not associated with suicidal IP. This lack of association in our study contrasts with other findings18 and might be related to the fact that study subjects, being illegal drug users, may have higher suicidal risk for this than for their alcohol risk use. Actually, in the above cited revision of cohort studies,18 subjects dependent on illicit drugs had a higher risk of suicide than subjects with alcohol dependence when compared to the general population.

The 32.7% prevalence of suicidal IP in illicit drug users from drug treatment facilities was noticeably higher than in the general population. In an Italian general population study the prevalence of ideations was 3% and plans 0.7%.19 Similarly, in a USA general population study, 3.7% of subjects had serious thoughts of suicide (ideation) and 1% suicidal plans.20 Reported prevalences of suicidal ideation or plans among illicit drug users vary, and this might be related to recruitment site or substance used. In a sample of users with any substance use disorder, taken from the general population, 23.4% reported suicidal ideation and 7.9% plans,21 slightly lower than in the present study. Cocaine and heroin users recruited in the community showed a prevalence of 27% of suicidal ideations;22 while subjects who had used psychotropic drugs recruited from treatment facilities, reported a lifetime prevalence of planned suicide with ideation of about 41%.23 As in our case, no sex differences in suicidal ideations were found in the study by Havens et al.22 while Darke and Ross24 found sex differences among patients in methadone treatment, females reporting more suicide attempts than males.

As in previous studies men in the sample were more active in illegal drug market activities than women.25,26 Additionally, men engaging in drug trafficking were more likely to have suicidal IP, which was not the case for women. Even though a considerable number of women reported drug trafficking, and in a context of illegal drug consumption drug trafficking and illegal/marginal IGA are closely related, only being involved in marginal IGA was independently associated with suicidal IP for both sexes. In contrast, having been in prison was positively associated with suicidal IP only in women, while for men it was the opposite. This finding among women would be in accordance with the fact that prisoners have higher rates of suicidal behaviors than the general population,26 and that women recently released from prison were 36 times more likely to die by suicide within one year of their release.27

Violent aggressive events usually become a traumatic experience28 because the physical and psychological impact of violence to the victim can be devastating.29 Several studies have shown that drug use-related violence was highly prevalent among drug users.20,30 Crime and violence are frequent in an illegal drug market environment, and they have been associated with suicidal behavior among substance users.14 Accordingly, in our study, having suffered recent violent traumatic experiences as a result of physical, psychological and/or sexual aggression, in the same period as suicidal IP, was identified as a clear risk factor for suicidal IP proneness for both sexes. Other studies which have assessed similar traumatic experiences over different periods, such as childhood or lifetime, reported similar results globally, also among drug users in treatment.23 Also Rossow and Lauritzen31 reported an elevated prevalence of suicidal behavior and ideation among drug addicts (42% in the previous month), which increased with the number of areas of childhood adversities.

Suicidal IP prevalence among illicit drug users in drug treatment facilities in our study is within the range of prevalences found among subjects with mental disorders. O’Neill et al.21 found a prevalence of suicidal ideations in subjects with mood disorders of 30.2% while for anxiety it was 25.6%. Even though effectiveness of suicide preventive interventions is difficult to assess due to the complexity of the phenomenon32,33 its higher prevalence among patients with psychiatric disorders is well accepted.34 Accordingly, clinical depression guidelines recommend assessing suicide risk in patients with depression.35 However, although clinical guidelines for suicide identify alcohol consumption and consumption of some other drugs as risk factors, in general, they don’t address treatment or specific programs for drug users. In fact, some of these guidelines do not include any substance use disorder, or even alcohol on their screening list. In our understanding, protocols should include assessing suicide risk in drug users to provide adequate treatment. Thus, this would not only be a matter of mental health centers but also of drug treatment centers.

The study provides evidence that the prevalence of suicidal IP among illicit drug users is high, especially among both men and women reporting recent violent traumatic experiences, being involved in marginal income generation activities and having been in psychological treatment. It also suggests the need, independently of the illegal substance taken, for suicide risk to be assessed in drug treatment centers in order to detect and prevent suicidal behaviors. Subjects with previous involvement in illegal drug market activities and crime deserve special attention. Effective suicide prevention strategies should be addressed to illicit drug users in treatment.

María Teresa Ruiz Cantero.

All authors participated in the study design and revised and improved successive versions of the manuscript. E. Arribas-Ibar conducted the statistical analysis, interpreted the results and wrote the first draft of the manuscript. A. Domingo-Salvany contributed to the statistical analysis, interpretation of results and manuscript writing. A. Sanchez-Niubò contributed to the statistical analysis and interpretation of results. M.T. Brugal reviewed the literature and contributed to interpretation of results. J.M. Suelves reviewed the literature and contributed to interpretation of results. All authors have approved the manuscript final version.

Funding for this study was provided by Spanish Government Grant: Instituto de Salud Carlos III -FIS PI11/01358. Further financial support was provided by the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR 2009 SGR 718) and FIS-Redes de investigación cooperativa RD12/0028/0018 and RD16/0017/0013. The EU project JUST/2010/DPIP/AG/1410 also contributed to survey implementation. FIS, AGAUR and EU-JUST grants had no role in the study design, collection, analysis or interpretation of the data, writing the manuscript, or the decision to submit the paper for publication. EAI was involved in the European Science Foundation research network programme ‘REFLEXION’-09-RNP-049.

The authors declare they have no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.