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Hockenhull JC, Whittington R, Leitner M, et al. A Systematic Review of Prevention and Intervention Strategies for Populations at High Risk of Engaging in Violent Behaviour: Update 2002–8. Southampton (UK): NIHR Journals Library; 2012 Feb. (Health Technology Assessment, No. 16.3.)

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A Systematic Review of Prevention and Intervention Strategies for Populations at High Risk of Engaging in Violent Behaviour: Update 2002–8.

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3Overview of the literature

Selection of included studies

As shown in Figure 1, the electronic searches identified 127,550 citations. After deduplication, both within and between the databases, 102,267 citations had the inclusion criteria applied at stage one. This resulted in 96,077 citations being excluded, 246 of which were reviews.

FIGURE 1. Flow diagram of inclusion of studies.

FIGURE 1

Flow diagram of inclusion of studies.

As a result of searching the reference lists of the 246 reviews, an additional 38 references were identified. Therefore, a total of 6240 papers had the inclusion criteria applied at stage two.

The process of applying stage two inclusion criteria resulted in 3760 references being excluded from both the intervention and risk reviews and a further 2053 being included in the risk review only. The remaining 326 papers met the inclusion criteria for the intervention review and data were extracted. At data extraction, 120 of the 326 papers were identified as not reporting any statistical analysis, mainly because of qualitative designs, and were therefore excluded from the review. A further 11 papers were identified as reporting data that were reported in other included papers. The primary paper for each study was retained, with any additional data reported in the linked paper combined, while the linked paper itself was excluded. A list of included papers is shown in Appendix 2, Table 55, and a list of excluded papers available on request.

Of the 195 included papers, three included more than one study, resulting in 198 studies being data extracted. All of the following analyses will be reported by study rather than by paper.

Different sections of the report require different selections of studies, as described throughout the report. However, Table 4 summarises the number of studies for each level of analysis.

TABLE 4. Number of studies included at each level of analysis.

TABLE 4

Number of studies included at each level of analysis.

Quality assessment

Design of studies

Of 198 studies, 51 (25.8%) were RCTs, one-third (33.3%) were concurrent/cross-sectional group comparisons and 68 (34.3%) were before/after study comparisons. The remaining 13 studies were crossover comparisons, correlational studies and experimental case studies (Table 5).

TABLE 5. Design of studies.

TABLE 5

Design of studies.

Length of follow-up

The maximum length of follow-up was reported by 179 studies and ranged from half an hour to 14 years, with the average length of follow-up being: mean = 524.26 days, median = 183.40 days and mode = 365 days (Figure 2).

FIGURE 2. Total length of follow-up in days.

FIGURE 2

Total length of follow-up in days.

Attrition

Attrition was calculable for 189 of the studies: 67 (35.4%) reported no attrition and four (2.1%) more than 80% attrition (Figure 3). The mean attrition was 20.0% and the median was 9.9%.

FIGURE 3. Attrition rates.

FIGURE 3

Attrition rates.

Intention to treat

The 198 studies included in the review reported on 728 comparisons. Of these, 31.9% were analysed on an ITT basis, 59.1% were not analysed on an ITT basis and 9.1% did not state whether they were ITT analysis or not (Table 6).

TABLE 6. Number and percentage of analyses reporting an ITT analysis.

TABLE 6

Number and percentage of analyses reporting an ITT analysis.

Baseline equivalence

Of the 120 studies comparing different study groups, equivalent baseline measures of aggression were reported for 51 (42.5%) studies. A further 11 reported equivalence on some measures of aggression and 16 (13.3%) reported non-equivalence. Twenty studies reported the baseline levels of aggression for each group but did not compare them statistically and 22 (18.3%) did not report any baseline measure of aggression (Table 7).

TABLE 7. Equivalence of baseline measures of aggression.

TABLE 7

Equivalence of baseline measures of aggression.

Blinding

Given the nature of many of these studies it is not surprising that blinding was not stated in the majority of papers, as for practical reasons this is impossible to achieve when evaluating psychosocial interventions. Where it was stated, it was most frequently reported for patients and the interventionist, with 10.1% of patients not being blinded and 14.6% being blinded, and interventionists not being blinded in 12.1% of studies and blinded in 12.6% of studies (Table 8).

TABLE 8. Blinding reported in studies.

TABLE 8

Blinding reported in studies.

Study characteristics

Number of studies

The number of studies published was relatively steady across the years, with an average of 32 papers being published each full year (Figure 4).

FIGURE 4. Number of studies by year of publication.

FIGURE 4

Number of studies by year of publication. a The year 2008 was a partial year

Country in which studies were conducted

Studies were conducted in 21 different countries, with only three studies being multinational, i.e. participants from more than one country. The majority of studies were conducted in the USA (55.1%), with the UK being the second most common location (10.6%), followed by Canada (6.6%) (Table 9).

TABLE 9. Number of studies conducted in each country.

TABLE 9

Number of studies conducted in each country.

Participant characteristics

Details of the characteristics of people included in the studies are shown below (see Tables 1014 and Figures 57).

TABLE 10. Average ages and age ranges of participants.

TABLE 10

Average ages and age ranges of participants.

TABLE 14. Number and percentage of studies reporting on substance abuse.

TABLE 14

Number and percentage of studies reporting on substance abuse.

FIGURE 5. Number of participants in complete data set.

FIGURE 5

Number of participants in complete data set.

FIGURE 7. Percentage of participants who were Caucasian.

FIGURE 7

Percentage of participants who were Caucasian.

Number of participants

The number of people approached to take part in the studies was reported in 94 (47.4%) of studies and ranged from 1 to 8325. The number of participants enrolled was reported in 191 (96.5%) of studies and ranged from 1 to 10,753. The number of participants at the end point of the study was reported in 196 (99.0%) of studies meaning that two studies failed to report the final number of participants in their study.

The studies reporting the final number of participants described a total of 51,258 individuals, the smallest study having one participant and the largest 10,753 participants (Figure 5). The majority (60%) of studies included ≤ 100 people.

Demographics of participants

The sex of participants was reported in 183 (92.4%) studies, with 95 (52%) studies including only males and 15 (8%) including only females. The percentage of males in the remaining studies ranged from 8% to 95% (Figure 6).

FIGURE 6. Percentage of participants who were male.

FIGURE 6

Percentage of participants who were male.

The average age of participants was reported in 166 studies (158 reported the mean age, four reported the median age and four reported both the mean and median age). The mean age ranged from 19 to 80.9 years, with SDs (reported by 118 studies) ranging from 1 to 15.9 years. The range of ages was reported by 70 studies (an additional study reported minimum age only). The minimum age of participants ranged from 13 and 65 years and the maximum age ranged from 32 to 97 years. Therefore, the youngest participant was 13 years and the oldest was 97 years (Table 10).

The percentage of participants who were described as Caucasian was reported in 98 studies, with six (6%) studies not including any Caucasian participants, and one study (1%) including only Caucasian participants. The percentage of Caucasian participants in the remaining studies ranged from 6% to 99% (Figure 7).

Population

Populations included in the review were either participants with a diagnosis of mental disorder, offenders, indictable offenders (i.e. those having committed indictable offences but not having been charged) or forensic participants (i.e. those with a diagnosis of mental disorder and offender/indictable offender status). The numbers of studies looking at each of these population types are shown in Table 11. Participants were mainly people with a mental disorder (38%) or offenders (35%), with those reported to have committed an indictable offence being studied in 15% of studies and offenders with a mental disorder (forensic) being included in 12% of cases.

TABLE 11. Number and percentage of studies reporting each population group.

TABLE 11

Number and percentage of studies reporting each population group.

Studies reporting on individuals with a diagnosis of a mental disorder (including forensic groups) reported a range of diagnostic groups, with patients defined as having an ‘other’ single mental health grouping being the most frequently reported (34%), followed by participants with a ‘mixed diagnosis’ (28%). Participants with personality disorders only were studied in 20% of the studies and participants with a diagnosis of schizophrenia or schizoaffective disorder only were studied in 11% of the studies (Table 12).

TABLE 12. Number and percentage of participants within each diagnostic group.

TABLE 12

Number and percentage of participants within each diagnostic group.

There were differences between the diagnosis of participants in the mental disorder group and the forensic group. Almost half of the studies investigating forensic participants reported mixed diagnoses, and a further 37.5% reported participants with an ‘other single mental health grouping’. Participants with a specific mental health diagnosis were reported in only 3 out of the 24 forensic studies (12.5%), whereas 32 out of the 75 studies (42.6%) examining participants with just a mental disorder reported investigating participants with specific mental disorder diagnoses.

The index offences that participants had committed differed greatly between the three groups. Offender participants had been charged with predominantly DV (44.3%), followed by mixed group of offences (28.6%) and sex offending (22.9%). For studies including forensic participants, mixed groups of offences were more frequently reported (41.7%), followed by sex offending (29.2%). A further 20.8% of studies did not report what offences participants had committed.

As expected, in the indictable group, DV was the most reported offence type (65.5%), with other indictable offences being reported in 24.1% of studies (Table 13).

TABLE 13. Number of participants within each offence category by sample group.

TABLE 13

Number of participants within each offence category by sample group.

Substance abuse

Substance abuse by participants was poorly reported in most studies, with only 43.4% (86) of papers reporting whether current substance abuse was or was not identified. Of the 86 studies reporting on substance abuse, 21 (24.4%) reported no substance abuse, five (5.8%) identified drug abuse, three identified (3.5%) alcohol abuse and 33 (38.4%) both alcohol and drug abuse. A further 24 (27.9%) studies identified some form of substance abuse, but did not report on the nature, i.e. whether it was drugs or alcohol (Table 14).

Intervention characteristics

Types of interventions

Of the 198 studies, 74 (37.37%) were single-group designs and 124 (62.6%) compared two or more groups. Of the 124 using a comparator group, 29.8% compared two different types of treatment (head-to-head comparisons), 24.2% TAU, 14.5% a placebo, 12.9% compared subgroups of one treatment (e.g. completers vs non-completers) and 8.9% no treatment. The remaining seven studies used a historical control (3.2%) or self as a control (2.4%) (Table 15).

TABLE 15. Number and percentage of studies reporting different control groups.

TABLE 15

Number and percentage of studies reporting different control groups.

The types of intervention studied are shown in Tables 16 and 17. Half of included studies used a psychological intervention (50.5%) as the primary intervention, one-quarter used a pharmacological intervention (23.7%) and one-quarter another form of intervention (25.8%). The specific categories of intervention by comparison type are shown in Table 16 and the comparators used in head-to-head studies in Table 17.

TABLE 16. Type of interventions by comparator group.

TABLE 16

Type of interventions by comparator group.

TABLE 17. Types of intervention in head-to-head studies.

TABLE 17

Types of intervention in head-to-head studies.

Psychological studies were more likely to use single-group comparisons and pharmacological studies head-to-head or placebo comparators. Where head-to-head studies were used, the same categories of intervention were compared, i.e. psychological interventions compared with another psychological intervention, and pharmacological interventions compared with another pharmacological intervention.

Setting

The start and end settings are shown in Table 18. The term ‘setting’ here refers to the location where the intervention is conducted and in the case of ‘community’ under what conditions, i.e. a probation order, or under the supervision of a mental health practitioner or neither (e.g. a person concerned about their propensity for violence who is offered a self-help intervention). The most frequently reported setting was community with people on probation (18.7%), followed by penal institutions (16.2%), community (14.6%) and community mental health (12.1%). The majority of studies (87.9%) had the same start and end setting. Of the 24 studies reporting different start and end settings, 12 were studies that started in penal institutions but ended in either the community or in mixed settings.

TABLE 18. Start and end settings of studies.

TABLE 18

Start and end settings of studies.

When start settings for the interventions are examined by intervention type (Table 19), it can be seen that studies in a forensic mental health setting mainly studied behavioural and cognitive therapies (75.0%), as did penal institutions (56.3%), community (44.8%), mixed settings (33.3%) and other settings (40.0%), whereas community probation settings used DV programmes. Pharmacological interventions were the focus of the majority of studies in community mental health settings (58.0%), accident and emergency (A&E) settings (100%), mixed settings (33.3%) and studies where the setting was unclear or not stated (40.0%).

TABLE 19. Setting and types of intervention.

TABLE 19

Setting and types of intervention.

Level of intervention

The levels of interventions for each of the types of intervention are shown in Table 20. Pharmacological interventions were by design at an individual level, whereas the psychological interventions were generally at the small group level.

TABLE 20. Level of intervention by intervention type.

TABLE 20

Level of intervention by intervention type.

Randomised controlled trials

In total, 51 RCTs, reporting on 197 comparisons between active interventions and/or active interventions plus placebo or other inactive control, were identified in the literature. These studies represent 25.8% of all intervention studies identified as meeting our inclusion criteria.

Predictably, studies meeting the design criteria of prospective RCTs were also not entirely representative of the empirical literature as a whole. The differences between the RCTs and the other studies are outlined below.

Quality

On variables used to assess methodological quality of studies, the RCTs reflected what was found in the whole data set (see Quality assessment) for baseline equivalence [χ2 = 2.347, degrees of freedom (df) = 3, p = 0.504] (Table 21), and sample attrition (Mann–Whitney U-test, p = 0.568) (Table 22). However, the total length of follow-up reported in studies was significantly longer in the non-RCTs (mean 629 days, SD 932, median 364 days) than in the RCTs (mean 253 days, SD 731, median 84 days) (Mann–Whitney U-test, p < 0.0001) (see Table 22) and the number of studies using some form of blinding to the intervention was far higher in the RCT data set (58.8%) than in the non-RCTs (6.1%) (χ2 = 66.486, df = 1, p < 0.0001) (see Table 21). Of the 197 comparisons conducted in the RCT studies, 53.3% used an ITT analysis, whereas only 27.2% of the 464 comparisons reporting whether an ITT analysis was used in the non-RCT data set used an ITT analysis (χ2 = 41.578, df = 1, p < 0.0001) (see Table 21).

TABLE 21. Categorical quality variables in RCTs and non-RCTs.

TABLE 21

Categorical quality variables in RCTs and non-RCTs.

TABLE 22. Continuous quality variables in RCTs and non-RCTs.

TABLE 22

Continuous quality variables in RCTs and non-RCTs.

Trial and participant characteristics

The distribution of the number of papers being published in each year was the same for RCTs and non-RCTs (χ2 = 3.629, df = 6, p = 0.774) (Table 23), as was the distribution of the number of participants in the studies (Mann–Whitney U-test, p = 0.422), mean age (Mann–Whitney U-test, p = 0.084), proportion of sample who were Caucasian (Mann–Whitney U-test, p = 0.436) (Table 24), the reporting of substance abuse (χ2 = 2.347, df = 3, p = 0.05) and the types of offences offenders had committed (statistical analyses not appropriate) (see Table 23) (see Study characteristics and Participants characteristics for description of whole sample).

TABLE 23. Categorical trial and participant characteristic variables in RCTs and non-RCTs.

TABLE 23

Categorical trial and participant characteristic variables in RCTs and non-RCTs.

TABLE 24. Continuous trial and participant characteristic variables in RCTs and non-RCTs.

TABLE 24

Continuous trial and participant characteristic variables in RCTs and non-RCTs.

The country in which studies were conducted appeared to differ between RCTs and non-RCTs (see Table 23), most notably the proportion of RCTs that were conducted in the UK (3.9%) was lower than non-RCTs (13.0%) and RCTs were more likely to fail to report where the study was conducted than non-RCTs (13.7% vs 3.4%, respectively). RCTs also reported a lower percentage of males (mean 55.02%, SD 38.76) than non-RCTs (mean 83.0%, SD 26.06) (Mann–Whitney U-test, p < 0.0001) (see Table 24).

The populations in the studies also appeared different in the RCTS and non-RCTS (see Table 23). RCTs focused primarily on participants with mental disorder (66.7%) compared with non-RCTs (27.9%), whereas non-RCTs included offenders in 40.8% of studies compared with 17.6% of RCTs. Only one (2.0%) RCT included forensic patients, whereas 16.3% of non-RCTs included forensic patients.

The diagnoses of participants in studies investigating a population of people with a mental disorder seemed to differ between RCTs and non-RCTs (see Table 23), with RCTs focusing on participants with a personality disorder (38.2%) and non-RCT studies participants with other single mental health grouping (38.5%).

Intervention characteristics

As expected, the types of comparisons differed between RCTs and non-RCTs, with nearly half of the non-RCTs reporting single group comparisons (49.3%) (Table 25).

TABLE 25. Categorical intervention characteristic variables in RCTs and non-RCTs.

TABLE 25

Categorical intervention characteristic variables in RCTs and non-RCTs.

As shown in Table 25, the type of primary intervention being tested in the studies also differed between RCTs and non-RCTs (χ2 = 43.611, df= 2, p < 0.0001), with 56.9% (n = 29) of RCTs evaluating pharmacological intervention alone, and only 21.6% of studies (n = 11) evaluating a psychological intervention. This compares with 12.2% of non-RCTs testing a pharmacological intervention and 60.5% a psychological intervention. Within each of the four broad categories of primary interventions, the specific groupings of primary interventions had too few studies for statistical analyses.

The setting that interventions were started in appeared to differ between RCTs and non-RCTs. RCTs were more likely to fail to report the type of setting (11.8%) compared with non-RCTs (2.7%), and were more likely to be conducted in community mental health settings (RCTs 19.6%, non-RCTS 9.5%). In contrast, non-RCTs were more likely than RCTs to be conducted in a penal institution (non-RCTs 19.7%, RCT 5.9%) or on community probation (non-RCTs 22.4%, RCTs 7.8%) (see Table 25).

The level the intervention was conducted on also appeared to differ between RCTs and non-RCTs. RCTs were primarily conducted at the individual level (67%), probably reflecting the focus on pharmacological interventions, whereas non-RCTs were more frequently conducted in small groups (46%) (see Table 25).

© 2012, Crown Copyright.

Included under terms of UK Non-commercial Government License.

Bookshelf ID: NBK97421

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