PONE-D-19-31703

Crystalline methamphetamine (ice) use prior to youth detention: A forensic concern or a public health issue?

PLOS ONE

Dear Dr Shepherd,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

I have read the paper and agree with the reviewers that it makes a useful contribution to limited evidence in this important area. The study is methodological sound with the use of linkage data however I felt it was lacking in detail in several areas (e.g., in relation to the databases used). I believe addressing this would strengthen the paper given the international readership of this journal.

The abstract needs to be clearer in the results section that CM was not associated with re-offending (i.,e., post-release) as this was one of the 2 main aims of the study.

Please add ethics approval reference

More information is needed on how mental health diagnoses are made, i.e., how they get recorded in RAPID. It may also be worth noting in the limitations section that these may an underestimate if they had mental health issues that had gone undetected/not diagnosed. Similarly how were de-identified records examined with Victoria Police) - was there a statistical linkage key used?

Please clarify why violent offending data time period was so variable - up to 18 months is reported in the method but the range indicated in the results sections suggests it was as early as 1-month for some - surely this would limit the chances of there being a reported offence?

The discussion could go further in unpacking the demonstrated relationship between psychiatric diagnosis and reoffending (e.g., poor impulse control, lack of insight etc).

I also think the paper would benefit from my consistent methodology - (recidivism, re-offending, future violent criminal offending).

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Reviewers' comments:

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Reviewer #1: Partly

Reviewer #2: Yes

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Reviewer #1: No

Reviewer #2: Yes

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Reviewer #1: No

Reviewer #2: No

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Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

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Reviewer #1: This study sought to identify (a) the lifetime prevalence of crystalline methamphetamine (CM) use, (b) the correlates of CM use, and (c) the association between CM use and future violent criminal offending among a sample of young people in detention. The participants were 202 young people in youth detention in the state of Victoria, Australia. Results revealed that more than one-third of the sample (38%) reported lifetime CM use, with older age, male gender, polysubstance use, and high levels of community disorganization being associated with CM use. The presence of a psychiatric diagnosis over the lifetime was not significantly associated with CM use, and CM use was not significantly associated with violent offending.

Given the media attention focused on the perceived relationship between CM use and offending, particularly violent offending, an empirical investigation of the relationship has obvious scientific merit. The authors should therefore be commended for undertaking this research. This study has several strengths, including a convincing rationale, a clear design and methodology, straightforward statistical analyses, and a solid synthesis of the results with the existing literature. I also appreciated the use of precise language that did not imply causality. Despite these strengths, there are several notable methodological limitations and several aspects of the manuscript in need of attention.

(1) The likely lack of generalizability of the study findings is a significant concern, particularly in light of the stated goals of the study. The sample size is relatively small (N = 202), with an even smaller subset (n = 76) who reported lifetime CM use. Also, the sample was drawn from two youth justice facilities in one Australian state. The small, geographically limited sample raises concerns that the sample may not be representative. The manuscript appropriately acknowledged that “it was not possible to formally assess sample representativeness” (see Limitations), but it is difficult to overlook this limitation. A stated study goal was to assess lifetime prevalence use of CM, but to do so in a meaningful and defensible manner requires a larger, representative sample.

(2) The manuscript indicates that informed consent was obtained from all participants over age 18, and that consent for participants under age 18 fell within the “mature minor” concept. However, there is no indication of whether anyone refused to provide informed consent, or whether any of the participants under age 18 were determined to lack the capacity to understand the nature of the study.

(3) A related concern is the lack of information regarding the recruitment fraction. The manuscript states that the authors achieved a “high recruitment fraction” (see Limitations), but no other information is provided. As such, it is not possible to assess whether the sample size of 202 is a small, moderate, or large sample of the population of interest. Providing the census of the two facilities would be informative.

(4) The use of a binary variable for CM use (0 = no CM use; 1 = lifetime CM use) lacks sufficient specificity and sensitivity. When addressing this limitation, the manuscript stated: “Firstly, we examined only lifetime use of CM and did not include measurements of frequency of use, use within a specified period (e.g., past 12 months), or estimates of typical quantity used” (see Limitations). Acknowledging this limitation is laudable, but it is difficult to overlook. Given the binary nature of this variable, participants who used CM once are grouped with participants who used CM many times. Such a crude classification system does not acknowledge the differences that (likely) exist between those with limited CM use and those with extensive CM use; grouping them together adds too much noise to the data, and the study results pertaining to CM use, the relationship between CM use and other drug use, and the relationship between CM use and violence become less defensible and less meaningful. For example, concluding that more than one-third of the sample reported lifetime CM use could be misleading because we do not know what proportion of those participants used CM once versus many times. To be clear, using CM once is indeed lifetime CM use, but it may not make sense (given what we know about episodic versus chronic CM use) to group one-time CM users with chronic CM users.

(5) There is a similar sensitivity problem related to the definition of violent offending. The manuscript defined violent recidivism as “any personal injury transgression that led to a police charge,” which included “acts intended to cause or threaten to cause physical harm to a victim.” There are two concerns. First, defining recidivism based on charges, as opposed to arrests or convictions, would benefit from being justified. Second, combining acts with threats introduces noise into the data because there are differences between acts of violence and threats of violence. Some justification for combining acts and threats would strengthen the manuscript.

(6) The manuscript does not include an a priori statistical power analysis. The manuscript mentions that the “modest sample size limited statistical power,” but (a) it is not clear how the authors know that statistical power was in fact limited, and (b) the lack of a power analysis (and potentially low power) raises concerns about Type II errors.

(7) The manuscript does not include any testable hypotheses.

(8) To support the assertion that the adolescent brain is still developing, the manuscript cites an article from 1999. The 1999 article is certainly a solid reference, but perhaps a more recent reference that reflects the current brain science would be more informative.

Thank you for the opportunity to review this manuscript.

Reviewer #2: This study reports on the association between a lifetime history of methamphetamine use and violent offending in a prospective study of people in youth detention. No previous studies have examined this relationship longitudinally in this population (see recent systematic review by McKetin et al in eClinicalMedicine 16: 87-91).

The main weakness of the present study is the exposure measure (any lifetime use) lacks the ability to differentiate between people who have used frequently and those with only occasional use. Its main strength is the used of linkage data for the outcome. The methods and results are clearly written, and the analytic approach appears sound.

Comments are minor:

1. Section 2.1 needs more information about the sampling frame & sampling strategy- how were participants selected?

2. Regarding the associations between having a psychiatric diagnosis and violent recidivism, is it possible this could be explained by reverse causation- that is, violent offences led to psychiatric assessment which then resulted in a diagnosis being recorded?

3. The comment “Our findings suggest that CM use on its own is unlikely to be an important consideration” etc over-reaches what this study shows, since it’s possible the association with violence is confined to people who have used CM frequently (see Foulds et al- “Methamphetamine use and violence: findings from a longitudinal birth cohort”- Drug and Alcohol Dependence, in press). Thus an alternative conclusion would be that more detailed assessment of CM use- ie frequency, route of administration and presence of substance use disorder- is necessary to aid treatment selection. Though it is noted that no evidence-based treatments specific to methamphetamine use disorder exist at this time.

4. In Table 2, 3 and 4 the inclusion of rows for the reference categories (eg “no cannabis”) is perhaps not necessary. Consider omitting the reference category rows unless these are essential to the data presentation.

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Reviewer #1: No

Reviewer #2: Yes: James Foulds

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Crystalline methamphetamine (ice) use prior to youth detention: A forensic concern or a public health issue?

PONE-D-19-31703R1

Dear Dr. Shepherd

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.

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