GLOSSARY
Specialised terms and abbreviations are used throughout this report. The meaning is usually clear from the context but a glossary is provided for the non-specialist reader. In some cases usage differs from that found in the literature, but each term has a constant meaning throughout the report.
Axis 1 Disorders
Classification system used to describe predominantly mood disorders such as depression or anxiety.
Case-control study
A study that compares two groups of people: those with the disease or condition (cases) and a very similar group of people who do not have the disease or condition (controls). The condition in this review would be suicidal behaviour. Researchers explore medical and lifestyle histories of the people in each group to learn what factors may be associated with the disease or condition.
Cohort study (also called longitudinal study)
A study that follows a group of people over time and assesses outcomes (such as suicidal behaviour) and particular risk factors
Confidence interval ( CI)
The range within which the "true" value (e.g. size of effect of an intervention) is expected to lie with a given degree of certainty (e.g. 95% or 99%). Note: Confidence intervals represent the probability of random errors, but not systematic errors (bias).
Cross-sectional study
A study in which the presence or absence of disease or other health-related variables (e.g. suicidal behaviour) are determined in each member of the study population at a single point in time.
Deliberate self-harm
Acts of intentional self-harm, irrespective of intent to complete suicide, that do not have a fatal outcome.
Generalisability (synonyms: applicability, external validity, relevance, and
transferability)
Generalisability is the degree to which the results of a study or systematic review can be extrapolated to other circumstances, in particular to routine health-care situations.
Methodological quality (synonyms: validity, internal validity, and quality)
Extent to which the design and methodology of a trial are likely to have prevented
systematic errors (bias). Variation in quality can explain variation in results of trials
included in systematic reviews. More rigorously designed (better 'quality') trials are more likely to yield results that are closer to the 'truth'.
Odds ratio ( OR)
The ratio of the odds of an event in the experimental (intervention) group to the odds of an event in the control group. Odds are the ratio of the number of people in a group with an event to the number without an event. Thus, if a group of 100 people had an event rate of 0.20, 20 people had the event and 80 did not, and the odds would be 20/80 or 0.25. An odds ratio of one indicates no difference between comparison groups. For undesirable outcomes an OR that is less than one indicates that the intervention was effective in reducing the risk of that outcome. When the event rate is small, odds ratios are very similar to relative risks.
Para-suicide
Acts of intentional self-harm (usually with intent to complete suicide) that do not have a fatal outcome.
P-value
The probability (ranging from zero to one) that the observed results in a study could have occurred by chance. In a meta-analysis the p-value for the overall effect assesses the overall statistical significance of the difference between the population group and control groups, whilst the p-value for the heterogeneity statistic assesses the statistical significance of differences between the effects observed in each study.
Protective factor
Societal or psychosocial conditions or individual behaviours that lessen the likelihood that an individual will die by suicide.
Qualitative study
A study which uses interviews, focus groups or any other non-quantitativemethodology to explore peoples' understanding and experiences of particular issues.
Relative risk ( RR)
The ratio of the suicide rate in persons exposed to a risk factor relative to that in people who are unexposed.
Risk Factor
Individual behaviours, psychosocial or societal conditions that increase the likelihood that an individual will die by suicide.
Risk group
Those known to be at elevated risk of suicide and suicidal behaviour.
Standardised mortality ratio ( SMR)
The standardised mortality ratio ( SMR) is the ratio of observed deaths to expected deaths according to a specific health outcome in a population. The figure for observed deaths is obtained for a particular sample of a population (e.g. suicides among drug misusers). The figure for expected deaths reflects the number of deaths for the larger population from which the study sample has been taken (e.g. suicides in the total population). The calculation used to determine the SMR is simply: (number of observed deaths/number of expected deaths) x 100. An SMR of 100 indicates that the age-standardised mortality rate in the group being studied is the same as the overall population. A ratio less than 100 indicates a lower than average death rate, while a rate of over 100 is higher than average.
Statistical significance
An estimate (usually expressed as a p-value) of the probability of an association (effect) as large as or larger than what is observed in a study occurring by chance. The cut-off for statistical significance is usually taken at 0.05, but sometimes at 0.01 or 0.001. These cut-offs are arbitrary and have no specific importance.
Suicide
Death resulting from an intentional, self-inflicted act.
Suicidal behaviour
Comprises both suicide and acts of self-harm that do not have a fatal outcome.
Suicidal ideation
Comprises thoughts about suicide, which may be as detailed as a formulated plan, without the suicidal act itself.
Systematic review (synonym: systematic overview)
A review of a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyse and summarise the results of the included studies.