Suicide 2
The psychology of suicidal behaviour
Rory C O’Connor, Matthew K Nock
The causes of suicidal behaviour are not fully understood; however, this behaviour clearly results from the complex
interaction of many factors. Although many risk factors have been identified, they mostly do not account for why
people try to end their lives. In this Review, we describe key recent developments in theoretical, clinical, and empirical
psychological science about the emergence of suicidal thoughts and behaviours, and emphasise the central importance
of psychological factors. Personality and individual differences, cognitive factors, social aspects, and negative life
events are key contributors to suicidal behaviour. Most people struggling with suicidal thoughts and behaviours do
not receive treatment. Some evidence suggests that different forms of cognitive and behavioural therapies can reduce
the risk of suicide reattempt, but hardly any evidence about factors that protect against suicide is available. The
development of innovative psychological and psychosocial treatments needs urgent attention.
Suicide is the 14th leading cause of death worldwide,
responsible for 1·5% of all mortality. Although
psychological factors such as risk taking and decision
making can affect the risk of other causes of death (eg,
heart disease and cancer), suicide is perhaps the cause of
death most directly affected by psychological factors,
because a person makes a conscious decision to end his or
her own life. Therefore, understanding of suicide and
develop­ment of methods to predict and prevent its
occurrence are the responsibility of psychologists, psych­
iatrists, and related mental health professionals. Earlier
reports have provided general reviews of the problem of
In this Review, we assess and syn­thesise existing
know­ledge about the psychology of suicidal behaviour,
including psychological theories of suicidal behaviour, risk
and protective factors, psycho­logical inter­ventions, and
key directions for psychological research into this
important topic.
The purpose of this Review is to provide a summary of
some of the most exciting and (in our view) important
findings about the psychology of suicidal behaviour.
Notably, space constraints preclude us from attending to
the full breadth of psychological factors that can
contribute to suicidal behaviour, and the full depth of
what is known at present (panel 1); this Review is not a
final exhaustive report of existing knowledge, but instead
an introduction to the psychological factors involved in
Although the specialty has grown substantially
in the past few decades, most psychological scientific
research thus far has focused on suicide ideation and
suicide attempts rather than deaths by suicide.
Investigators of an epidemiological study
of suicidal
behaviour in 17 countries documented the lifetime
prevalence of suicide ideation (9·2%), plans (3·1%), and
non-lethal attempts (2·7%). Prevalence estimates vary
widely by country; however, once present, the character­
istics of suicidal behaviour are quite consistent across
different countries. For example, the onset of suicide
ideation increases strikingly during adolescence in every
country studied.
Additionally, cross-nationally, about a
third of people who think about suicide will go on to make
a suicide attempt, and more than 60% of these transitions
occur during the first year after initial onset of suicide
This finding is consistent with a continuum
approach, with suicide risk increasing as an individual
moves through ideation and planning to attempts.
Multifactorial causes and the role of psychiatric
The causes of suicidal behaviour are not fully understood;
however, this behaviour clearly results from complex
interaction of many different factors. The risk of non-
fatal suicidal behaviour is increased in young people,
women (who have higher rates of non-lethal suicidal
behaviour than do men, although men are more likely to
die by suicide), people who are unmarried, and people
who are socially disadvantaged (eg, low income and
education, or unemployed).
Although a range of risk
factors for suicidal behaviour has been identified, how or
Panel 1:
Suicide is the act of an individual intentionally ending their
own life. We use the general term suicidal behaviour to refer
to thoughts and behaviours related to an individual
intentionally taking their own life. These thoughts include the
more specific outcomes of suicide ideation, which refers to an
individual having thoughts about intentionally taking their
own life; suicide plan, which refers to the formulation of a
specific plot by an individual to end their own life; and suicide
attempt, which refers to engagement in a potentially
self-injurious behaviour in which there is at least some
intention of dying as a result of the behaviour. We also refer
to self-harm, defined by the National Institute for Health and
Care Excellence as intentional self-poisoning or self-injury,
irrespective of motive.
May 2, 2014
This is the second in a
three papers about suicide
Suicidal Behaviour Research
Laboratory, Institute of Health
&Wellbeing, University of
Glasgow, Glasgow, UK
(Prof R C O’Connor PhD)
; and
Department of Psychology,
Harvard University, Cambridge,
(Prof M K Nock PhD)
Correspondence to:
Prof Rory C O’Connor, Suicidal
Behaviour Research Laboratory,
University of Glasgow, Academic
Centre, Gartnavel Royal Hospital,
Glasgow, G12 0XH, UK
For the
NICE clinical guidelines
on self-harm
see http://
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