The longitudinal association between lifetime mental disorders and first onset or recurrent suicide ideation

Suicide is a major global public health problem, with an estimated 800,000 suicides per year [1]. Although difficult to assess, it its estimated that for every person who died by suicide, there are around 20 people who attempted suicide. Suicide ideation are even more common. In different studies, the 12 months prevalence of suicide ideation was estimated to be around 3%, indicating that globally, each year millions of people consider life not worth living for at least a period of two weeks (e.g. Kessler et al., [2]; Ten Have et al., [3]). The association between a history of mental disorders and suicide and suicidal behavior (i.e. suicide ideation and attempts) is well established (e.g. Bolton and Robinson, [4]; Harris and Barraclough, [5]; Nock et al., [6]). Indeed, one of the most well established statistics in suicide prevention is that mental disorders play an important role in 90% of all suicides [7, 8]. Although this number has been up for debate [9], many cross-national population based studies confirmed the association between a history of mental disorders and suicide ideation, suicide attempts and completed suicides [4, 10, 11]. In high-income countries, after controlling for comorbidity, lifetime mood disorders such as major depressive disorders (MDD) were more strongly related to suicidal behavior in comparison to other disorders such as anxiety of substance use [11]. Most population-based studies are based on cross-sectional data, and therefore provide no information on the development of suicidal behavior over time [4, 10‐12]. Longitudinal studies are scarce, so we know relatively little about the sequential relationship between lifetime mental disorder and later onset or recurrence of suicidal behavior. Knowing which disorders are uniquely related to suicidal behavior over time is important for a better understanding, prediction and treatment of suicidal behavior [10]. Analysis of a community sample survey with a 13 year follow-up indicated that especially major depressive disorder (MDD) and substance abuse were related to the first onset of suicide ideation and suicide attempts, although the authors did not control for comorbidity [13]. A population based survey from the UK with an 18 month follow-up found that the presence of mental illness was the best predictor of the first onset of suicide ideation, although no formal diagnostic interviews were conducted [14]. A study using Dutch longitudinal population based data (NEMESIS-1), found that after adjustment for comorbidity, life events and vulnerability factors such as neuroticism, mood and anxiety disorders increased the odds of first onset suicide ideation and suicide attempts [3]. One hypothesis that aims to explain this prolonged vulnerability for suicide ideation after an initial episode of a psychiatric disorder comes from the differential activation model [15, 16]: during a psychiatric episode, an association is formed between sad mood and dysfunctional, negative thinking. After the initial episode, as soon as a recovered patient experiences any small change in mood, this almost automatically results in negative thinking and the activation of dysfunctional self-schema’s which increase the chance of suicide ideation. In the current paper, we used data of the second Dutch longitudinal population-based study (Netherlands Mental Health Survey and Incidence Study-2: NEMESIS-2), to estimate the longitudinal association of a wide variety of common mental disorders and suicide ideation after controlling for demographic variables and comorbidity.

Suicide and suicidal behavior are a complex phenomenon, and the end result of the interaction of psychiatric, psychological, biological and social factors [8, 17]. Information on the history of psychiatric disorders will therefore only provide a part of this complex picture. However, detailed information on for example key psychological constructs such as entrapment is often not available in a patient medical record, whereas history of psychiatric illness will be [18, 19]. Knowing which psychiatrist disorders are most strongly associated with suicide ideation over time will help professionals such as general practitioners to decide which patient should asked more in detail about suicide ideation and plans.

Given the evidence for the association of MDD and suicide ideation, and the high level of comorbidity of for example anxiety and personality disorders with MDD, we hypothesize that after controlling for other psychiatric disorders, MDD will have the strongest association with suicide ideation at follow-up.

The data used in this study comes from a population based psychiatric epidemiologic survey called the Netherlands Mental Health Survey and Incidence Study-2 (NEMESIS-2: De Graaf et al. [20]). It replicates and updates the first Netherlands Mental Health Survey and Incidence Study (NEMESIS-1: Bijl et al. [21]) conducted from 1996 to 1999. NEMESIS-2 is based on a multi-stage, stratified random sampling procedure of households, with one respondent randomly selected in each household. Data collection of the first wave (T0) started in November 2007 and lasted until July 2009 and resulted in 6646 respondents providing written informed consent and completing the assessment. The interviews were done by 98 professional interviewers of field work agency GfK. Given the sensitive topic of the interviews, they had to be at least 25 years old. Most interviews were administrated at the home of the respondent. Medical ethical approval was obtained from the national Medical Ethics Review Committee for Institutions on Mental Health Care (METC 12–255). The respondents were found to be representative of the general population, with a slightly underrepresentation of younger respondents. Three years after a respondent finished the first wave, he/she was approached for the second wave (T1). A total of 5303 persons (80.4%) could be interviewed again. A similar procedure was followed for the third wave: 3 years after T1, all respondents were again approached, resulting in 4618 (87.8%) persons to be re-interviewed. Except for bipolar disorder, attrition between T0 and T2 was not significantly associated with individual 12-month mental disorders or with lifetime suicidal behavior at T0. More details on the design and method can be found in de Graaf et al. [20].

In this study, we investigated the associations of lifetime axis-I and axis-II disorders and suicide ideation over time using data from a large Dutch population based sample (NEMESIS-2). We hypothesized that after controlling for the presence of other mental disorders, MDD would have the strongest association with suicide ideation over time compared to other disorders.

Around 2.9% (n = 132) of the participants showed suicide ideation at follow up, which is comparable to results from the first NEMESIS study [25]. We found that most psychiatric disorders were significantly related to suicide ideation over time when we did not control for comorbidity. However, when controlling for comorbidity, the only two disorders that had a significant association with suicide ideation at follow up were lifetime MDD and GAD. This indicates that although it might seem that every psychiatric disorder is related to the risk for suicide ideation over time, the additional predictive power of most diagnosis above and beyond MDD or GAD is neglectable [8]. As hypothesized, the association of MDD with suicide ideation at follow-up was twice as strong as the association of GAD with suicide ideation. After controlling for other disorders, the odd ratios for dysthymia, borderline personality disorder and any anxiety disorders dropped most sharply, reflecting their high level of comorbidity with MDD. The odds for GAD also dropped but stayed significant, suggesting that GAD does predict suicide ideation above and beyond MDD even though GAD is highly related to MDD.

The finding that a lifetime history of MDD and GAD were related to the onset or recurrence of suicide ideation indicates that particularly these respondents have a long-time vulnerability for suicide ideation. As stated in the introduction, this is in line with the differential activation hypothesis, that states that patients become more vulnerable for negative ideation and suicide ideation after an initial psychiatric episode due to the strengthening of the association between sad mood and negative thinking [15, 16]. For clinical practice, this indicates that patients with a history of MDD or GAD stay vulnerable for suicide ideation, even though they report no suicide ideation in the past 12 months. This group is at higher risk to develop suicide ideation even after only a mild decrease in mood. Primary care physicians or other gatekeepers should therefore carefully monitor patients with a (history of) MDD or GAD especially after new life stressors such as a divorce, as they are more vulnerable to develop suicide ideation.

Given the high prevalence of MDD, we found a high PARP of 47.8%. This suggests that if we would be able to effectively treat all participants with MDD, and prevent the recurrence of MDD, a reduction of 47.8% of the onset or recurrence of suicide ideation can be expected. This is in line with the rationale of the perfect depression initiative of the Henry Ford Health System Perfect Depression Care Program. After they adopted a program that optimized their treatment of depression, suicidal behavior, including actual suicides decreased substantially [26]. Indeed, training of gatekeepers and general practitioners (GP) in the recognition of participants with a high risk for (recurrent) depression and suicide ideation are at the core of the multifaceted community prevention programs European Alliance Against depression [27]. The training of GPs and gatekeepers, in combination with a public awareness campaign and a program for high risk groups lead to a significant decrease in suicidal behavior in both Germany [27] and Hungary [28]. The program is currently being implemented in the Netherlands [29].

After controlling for comorbidity, a lifetime history of MDD and GAD were related to suicide ideation at follow-up, indicating that these respondents have a long-time vulnerability for suicide ideation. For clinical practice, this indicates that patients with a history of depression or GAD stay vulnerable for suicide ideation, even though they do report suicide ideation in the past year.