A wide range of mental illnesses can contribute to the increased likelihood
of suicidal thoughts and attempts, but only those characterized by anxiety and
poor impulse control significantly predict who is more likely to act on
suicidal thoughts, according to a multinational study on mental health.
The study was published online in the open-access journal PLoS
Medicine on August 10 and was derived from data from the massive World
Health Organization (WHO) World Mental Health Survey Initiative. The
initiative is ongoing and has so far been carried out in 28 countries
throughout the world. The study included data from nearly 110,000 adults in 21
countries. Researchers analyzed the data to identify patterns of how suicidal
thoughts, plans, and attempts can be predicted by psychiatric disorders
preceding such thoughts and behaviors.
In this global initiative, trained research staff in each participating
country conducted face-to-face interviews with adults living in the community
and collected various data on the respondents' lifetime mental health
histories. The WHO Composite International Diagnostic Interview, a structured
questionnaire validated for assessing DSM-IV psychiatric disorders
across various countries and cultures, was the instrument used.
In developed countries, 52 percent of adults who had at least suicidal
ideation reported a prior psychiatric disorder, compared with 43 percent in
developing countries. Among those who made suicide attempts, the prevalences
of prior psychiatric disorder were 66 percent and 55 percent,
One of the surprising findings was that, although it has been widely cited
that over 90 percent of people who committed suicide have psychiatric
disorders, the rates of psychiatric disorders reported by people in this study
with suicidal ideation and attempts were lower than that, said the study's
lead author Matthew Nock, Ph.D., professor of the social sciences in the
Department of Psychology at Harvard University.
In an interview with Psychiatric News, Nock noted that the
apparent inconsistency between previous and current data may be explained by
several factors. First, it is difficult to make a postmortem psychiatric
diagnosis for people who have died of suicide, and thus previous studies may
have overestimated the presence of psychiatric disorders. Second, people who"
succeed" in suicide may have a higher rate of psychiatric
disorders than those who have made nonfatal attempts or have suicidal
thoughts. It is also possible that, beyond psychiatric disorders, "there
are other factors that contribute to suicide attempts," said Nock.
Analyzed separately, each psychiatric disorder, as identified by the
survey, was associated with an increased risk of a subsequent suicide ideation
or attempt compared with having no psychiatric disorders, the study authors
found. Most of the associations remained statistically significant in both
developed and developing countries after controlling for potentially
The magnitude of associations varied by the type of disorder and country
type, the study revealed. Mood disorders, including bipolar disorder,
depression, and posttraumatic stress disorder (PTSD), were the strongest
predictors of suicide attempts in developed countries. However, PTSD,
substance use disorders, and conduct disorder were the strongest predictors in
Perhaps because past research tended to concentrate in developed countries,
the importance of a history of conduct disorder is greatly underappreciated
and underresearched, Nock observed. "Clinicians and policy makers should
pay more attention to people with a history of conduct disorder in prevention
efforts," he said.
Another important predictor for suicidal attempts was the number of
comorbid psychiatric disorders, the study found. For example, in developing
countries, having one disorder was associated with a risk ratio of 3.9 for
suicide attempt compared with having no disorder, while having three disorders
was associated with a risk ratio of 14.2.
Despite more research efforts and public health attention on suicide
prevention, the incidence of suicide has declined much in the past two
decades, the researchers noted. "Because the population base rate for
suicide attempts is low, it is very difficult to study and requires a very
large sample," said Nock. The size of this worldwide survey, therefore,
was particularly valuable for conducting sophisticated analyses to help
understand the causes of suicide.
"One of the most unexpected findings was that, although depression
was among the strongest predictors of suicidal thoughts, it was not at all a
strong predictor of who is likely to progress from thoughts to
attempts," commented Nock. The study also found no association between
major depression and impulsive suicidal attempts.
Instead, the study found that PTSD, bipolar disorder, conduct disorder, and
substance use disorders were the strongest predictors of individuals with
ideation who were at higher risk of making suicide plans and attempts."
Only disorders characterized by anxiety and poor impulse control
predict which people with suicide ideation act on such thought," they
concluded in the report.
With new insights, Nock admitted, the study poses a number of questions,
including "Are there different mechanisms for suicidal thoughts and
suicide attempts?" He and his colleagues plan to conduct additional
analyses on the data to better understand the risk and protective factors
associated with suicidal behaviors, including lifespan risks and symptom
"We plan to drill down to what types of symptoms are more predictive
of suicidal behaviors, because many psychiatric disorders are quite
heterogeneous," said Nock.
"Cross-National Analysis of the Associations Among Mental
Disorders and Suicidal Behavior: Findings From the WHO World Mental Health
Surveys" is posted at<www.plosmedicine.org/article/info:doi%2F10.1371%2Fjournal.pmed.1000123>.▪