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Richardson R, Trépel D, Perry A, et al. Screening for psychological and mental health difficulties in young people who offend: a systematic review and decision model. Southampton (UK): NIHR Journals Library; 2015 Jan. (Health Technology Assessment, No. 19.1.)
Screening for psychological and mental health difficulties in young people who offend: a systematic review and decision model.
Show detailsThe purpose of this research was to apply rigorous systematic review and evidence synthesis techniques to answer the question, ‘What would be the benefits of carrying out a screening assessment for treatable psychological and mental health conditions in young offenders and in which groups might it be cost-effective?’
Current UK policy provides guidance on screening for mental health problems in young people who offend,23 as described in the previous chapter, but the clinical effectiveness and cost-effectiveness of the recommended screening pathways is largely unknown. There are, in fact, a number of ways in which screening pathways could be configured and a large number of uncertainties exist. The decision problem can be framed in terms of these uncertainties. A main aim of the review is to establish the extent to which existing evidence can reduce these uncertainties and to identify where future research should be targeted so that uncertainties can be further reduced.
Screening
One option for identifying mental health problems in young people who offend would be to offer this entire group a detailed diagnostic mental health assessment in the form of a gold standard interview conducted to internationally recognised criteria.26,27 There are advantages to this: all who were offered treatment would be in need of it and all of those not given treatment would not require it. Although such an approach would give perfect precision, it may not be feasible because it may require substantial resources to implement.
The use of screening instruments, which trade a saving in resources for a reduction in precision, is the typical alternative to such a strategy.11 Screening measures that have been used with young offenders can be divided into a number of broad categories: those that are designed to detect a specific mental health problem, such as major depression, and those that are designed to detect a general mental health problem or need.28 Often this maps onto a division in young offender measures between those instruments that provide diagnostic test accuracy data and those that identify a mental health need but do not establish the accuracy against a gold standard diagnostic interview.
A further division is into those measures that are specifically designed for use with a young offender population (e.g. MAYSI-2,10 CHAT mental health screen23) and those that are used with young offenders but which were originally developed for use in the wider population. A potential advantage of measures designed specifically for young offenders is that they may consider expected characteristics of the population (e.g. limited literacy) and may be designed for use by youth justice personnel with no formal mental health training. However, a potential disadvantage is that they may not have received the same level of psychometric evaluation as some of the more widely used measures.
Each screening instrument from these broad categories could be used in a number of ways to make a decision about a person’s mental health needs, including the need for treatment. Scores on a screening measure could be considered alone in making that decision, in combination with each other (e.g. a general screen for any mental health problem followed by a disorder-specific screen) or in combination with a gold standard (e.g. a general screen followed by gold standard interview for all those scoring positively on the screen).
Currently, there is uncertainty around which broad category of instrument is likely to be most effective (e.g. bespoke measures for young offenders vs. measures originally designed for use in the wider population) and within a category it is unclear if particular screening instruments are more accurate than others in identifying mental health problems. In addition, there is further uncertainty around whether a decision should be made on the basis of a single instrument or whether a combination should be used in a screening pathway.
Many screening instruments have a range of possible scores and so it is possible to identify different points along that range above which a person could be predicted by the screening instrument to have a mental health difficulty. As this cut-off point is varied, sensitivity and specificity will also change in a consistent way: as sensitivity increases, specificity will decrease (and vice versa).11 (For an introduction to methods of quantifying diagnostic test accuracy, including concepts such as sensitivity and specificity, see Appendix 1.) There is, then, always a balance to be struck: if sensitivity is high, specificity is likely to be low; if specificity is high, sensitivity is likely to be low. A decision needs to be made about what balance between sensitivity and specificity is likely to be appropriate in a particular decision context. There are no definitive guidelines but, as a general rule, when the clinical context involves screening, high sensitivity is usually valued over high specificity. If sensitivity is high, this means that few people who have a condition will be missed, even if this is at the expense of somewhat lower specificity. Ensuring that few people with the condition are missed is often an aim of a screening strategy. However, in many decision contexts – including screening for mental health problems in young people who offend – it may not be possible to ensure very high sensitivity. Screening measures for mental health problems can have substantial inaccuracies when assessed against a gold standard, which means that very high sensitivity on such instruments is likely to be associated with low specificity. A consequence of low specificity is a high false-positive rate, which can be problematic in a number of ways. For example, if screening is used in the absence of a confirmatory gold standard diagnosis, treatment may be offered to many people who do not in fact require it. This may be potentially damaging to the recipients and can have substantial costs attached to it for services. Even if a screening measure is followed by a confirmatory diagnostic assessment, it may be inefficient and prohibitively costly to refer on for that further assessment all people who score positive to a screen if that number contains a large number of false positives. As a very broad guideline, then, a cut-off on a screening instrument may be required that gives sufficiently high sensitivity while retaining moderate specificity.
Studies of diagnostic test accuracy typically evaluate the screening measure against a gold standard categorisation of those with and without the mental health diagnosis, regardless of whether or not the true cases are already known to services or are previously unidentified cases. In this particular decision context, the screening for mental health problems in young people who offend, screening may be of value only for the identification of previously unidentified cases, because known cases may already be receiving treatment. There are a number of uncertainties related to this distinction between known and unidentified cases. It is unclear if the diagnostic performance of the test may differ if restricted to the identification of previously unknown cases. It is also unclear if the characteristics of the previously unidentified cases and the already identified cases differ, and this may be of relevance to understanding the likely performance characteristics of a test when restricted to the identification of new cases. For example, it is possible that already known cases will be more severe and therefore easily identifiable in the absence of screening, whereas unidentified cases may be less severe. This may have consequences for the need to offer treatment or the type of treatment offered. The prevalence of unidentified cases is also unclear, and this may have consequences for the balance between true positives and false positives at a particular cut-off point on an instrument. This in turn may affect the selection of an optimal cut-off point and the balance it offers between sensitivity and specificity.
Additional features of the decision problem relate to uncertainties about the behaviour of professionals in terms of screening. For example, it is unknown whether or not professionals find particular instruments acceptable and whether or not the results from a screening measure have an impact on professionals’ behaviour, such as making a referral for a particular type of treatment.
Clinical effectiveness and cost-effectiveness
On the assumption that professional behaviour is altered by the results of a screening test, screening and referring are of use only if there is an effective and cost-effective treatment for the particular mental health problem. In terms of effectiveness there are a large number of uncertainties. These include whether or not interventions for mental health problems in young people who offend are clinically effective and cost-effective, whether or not improvements in mental health symptoms are related to changes in other outcomes, such as the likelihood of reoffending, whether or not the interventions are acceptable to this population and whether or not potentially effective interventions can be feasibly delivered in UK settings.
Setting
Young people who have offended may be in the community or incarcerated. In terms of the decision problem outlined above, each of the considerations applies separately to these two settings. It is possible, for example, that a distinct screening pathway may be more appropriate in one setting than in another.
Objectives
On the basis of this decision problem we developed five objectives related to diagnostic test accuracy, the clinical effectiveness and cost-effectiveness of screening and (more broadly) the clinical effectiveness and cost-effectiveness of interventions for mental health problems in young people who offend. These five objectives are to:
- conduct a systematic review and evidence synthesis of the diagnostic properties and validity of existing screening measures for mental health problems in young people who offend
- assess the clinical effectiveness of screening strategies in this population and (more broadly) the clinical effectiveness of interventions for mental health problems
- assess the cost-effectiveness of screening strategies in this population and (more broadly) the cost-effectiveness of interventions for mental health problems, with specific reference to identifying in which groups they may be cost-effective
- assess whether or not current screening strategies meet minimum criteria laid down by the UK National Screening Committee (NSC) in the light of this evidence synthesis
- identify research priorities and the value of developing future research into screening strategies for young offenders with mental health problems.
Structure of the report
We carried out a single comprehensive search to identify the evidence needed for this research. This search is described in Chapter 3. We then conducted the research in a number of interlinked phases in which we summarised the available literature on screening assessments for treatable psychological and mental health conditions in young offenders.
At each stage of the review and in the production of the final report we adhered to the relevant guidelines for the conduct and reporting of systematic reviews.29,30 The research is registered on the PROSPERO database (registration number CRD42011001466). A copy of the original protocol for the review is available alongside copies of this report on the National Institute for Health Research (NIHR) website (www.journalslibrary.nihr.ac.uk/).
Stakeholder involvement
We established an expert advisory group and two stakeholder groups. The expert advisory group consisted of academics with methodological expertise in the conduct of systematic reviews and content expertise in the criminal justice system. Members of this group were approached at various stages of the project to offer advice on specific questions.
One stakeholder group consisted of professionals working within the justice system. We sought to include professionals working in both community settings and the secure estate. We met with members of this stakeholder group at various stages of the project. A specific role of this group was to help establish current UK practice in the screening and treatment of mental health problems in young people who offend and more generally to clarify the nature of the decision problem.
A second stakeholder group consisted of young people (age range 10–15 years) from the National Association for the Care and Resettlement of Offenders (Nacro). We held two meetings with these young people to gather their views on a range of subjects relevant to the review, including the acceptability of different potential screening pathways and different types of interventions. The older members of this group were asked to comment and help draft the plain English summary.
Appendix 2 provides a list of the stakeholders and professionals who provided advice during the review process.
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