A large proportion of patients had desisted from crime 1 year following treatment initiation. Among those who continued their criminal involvement, there was still a significant reduction in the number of crimes committed. Our results indicate that whether treatment was interrupted, completed or ongoing was an important factor for desistance among OMT patients, but not necessarily among inpatients. Further, desistance was more likely for participants who during the study period had not used stimulants, left a substance using social network and improved their self-control score. In sum, this study confirms a link between desistance and recovery-related factors, such as treatment completion and retention, reduction in substance use, and changes in social network and self-control. On the other hand, the role of treatment completion and retention may vary depending on treatment type.
Treatment and desistance
Although reductions in crime following substance use treatment in itself is not a novel finding [
2,
6‐
9,
45,
46], we found several relationships between treatment factors and crime.
First, even among participants that continued criminal involvement, there was a significant reduction in the number of crimes committed. This underlines the importance of looking beyond complete desistance when investigating the effect of interventions on crime.
Second, inpatients had a higher prevalence of criminal involvement before treatment start. This could be related to the younger age in this patient group or the reported differences in substance use pattern, e.g. more polysubstance use and stimulant use. In adjusted analyses, inpatients were also more likely to desist compared to OMT patients. This could be a result of the described group differences between inpatients and OMT patients (such as substance use pattern), or it could be related to differences in treatment content.
Third, ongoing treatment was associated with desistance, which is in line with several previous studies [
12,
47]. However, the importance of treatment status may vary with treatment type. For inpatients, desistance rates were high regardless of treatment status, while nearly half of OMT patients with interrupted treatment continued crime. This could be due to differences in the patients that seek the different treatment types, but also due to differences in the two treatments. Inpatient treatment involves patients being physically removed from their previous day-to-day lives, patterns and social contexts [
48]. This treatment-intensity could contribute to a ‘flying start’ for changes in behavioural patterns, including criminal involvement. It is also possible that seeking inpatient treatment reflects a high motivational state, and that some treatment goals were achieved even when treatment was interrupted [
49]. OMT patients, on the other hand, typically receive outpatient treatment, often life-long, without immediate major changes in their daily lives or surroundings. When OMT was interrupted early, many patients may have found themselves in a very similar overall situation as when they entered treatment, resulting in a return to old patterns when it came to both substance use and crime. An unanswered question is whether this positive effect of inpatient treatment despite interruption will remain over time, given the relatively short follow-up period of this study.
Fourth, criminal involvement before treatment initiation may also affect treatment retention. OMT patients with no crime in the study period were more likely to be in ongoing treatment after 1 year, and participants with interrupted treatment had committed a higher number of crimes before treatment. It is possible that criminal involvement is a marker for a more severe over all situation for the participants, however, it has also been suggested that aspects of a criminal lifestyle can affect treatment engagement negatively [
50]. In the latter case, crime specific interventions may improve outcomes of substance use treatment for some patients.
Substance use pattern, social network and self-control
Overall, we see that participants who continued crime showed little change in substance use, social network and self-control. Participants that desisted, on the other hand, had positive changes and more closely resembled the no crime group at follow-up. This reflects both the possibility of positive change in these crime-related factors and how these changes co-occur with desistance from crime.
When controlling for a number of other substances, stimulant use has previously been associated with crime among substance users both in and out of treatment [
5,
51]. We found that participants with no use of stimulants in the study period were more likely to have desisted from crime or to be in the no crime group. There may be several reasons for the relationship between stimulant use and crime. Amphetamines, the most commonly used stimulant in this sample, can cause irritability, agitation, paranoid states, disorientation and compulsive behaviours [
52]. Subgroups of stimulant users have been found to be more risk-taking and sensation-seeking [
53], to be more impulsive/disinhibited [
53,
54], and to show impaired decision making [
55]. One study found poor quality decision making among chronic stimulant users, but not chronic opiate users [
56]. A pilot-study found stimulant users to have reductions in loss aversion, which could lead to disadvantageous decision making [
57]. It is possible that these traits or behaviours can be part of the explanation of the link between stimulant use and crime (risking the negative consequences of crime), whether the traits were present prior to stimulant use or emerged as a pharmacological effect (acute or degenerative) of the stimulant use. Stimulant users in treatment may thus need targeted interventions to improve substance use and crime outcomes [
51]. In addition, for OMT patients where treatment focus may be primarily on the opiate use, simultaneously addressing stimulant use could be important [
58].
Spending time with a substance using social network has previously been associated with increased likelihood of crime in substance users [
3,
5]. We found that leaving a substance using network was associated with desistance, and that participants with no crime in the study period were also more likely to have had no substance using network in the study period. This is in line with findings that social identity and group membership in social networks that provide positive values and resources, may be important for both recovery and desistance from crime [
10]. Further, the findings underscore the potential benefit of interventions that support development of new, non-using social networks [
3,
59], for instance through social skills training [
23]. Efforts to facilitate education, work and other activities with social contexts could provide both an arena for building social networks and meaningful daily activities which could have a positive effect on crime outcomes [
51] and recovery from dependence [
60].
We found an association between improved self-control score and desistance. There has been little research on the relationship between self-control and crime in substance using populations, although lower self-control has been associated with crime among substance using offenders [
61,
62]. Our finding supports the potential utility of including components or interventions that could boost self-control in substance use treatment as well as in the criminal justice system. There is ongoing work in identifying and evaluating feasible interventions that could, in supplement to traditional treatment, directly or indirectly support self-control. For crime outcomes, self-control training in jail has been associated with both increases in self-control and desistance [
63]. For substance use outcomes, self-control related interventions with promising results include goal management training, working memory training and cognitive bias modification [
64,
65]. Finally, self-control must be seen in context with situational factors. Sufficiently motivating and realistic goals are a prerequisite for self-control, and as articulated by Burt: “Deliberation and PFC [prefrontal cortex] processing are luxuries reserved for those people who are not cognitively overloaded with, for example, survival efforts, threats, or emotional duress” (26, p64).
Among substance users both in and out of treatment, polysubstance use has been linked to crime [
66]. In our study, the desisted crime group had a greater reduction in polysubstance use compared to the continued crime group, however, the results of the adjusted model were inconclusive. Our variable reflects the number of different substances used, but not the magnitude of the use (e.g. amounts, days of use per week). Thus we could not investigate whether reduction of substance use magnitude is effective in reducing crime, compared to complete abstinence [
16], which is a question of great relevance when determining the goals of substance use treatment.
Strengths and limitations
This study followed a relatively large cohort of participants who received comprehensive substance use treatment. The sample was naturalistic in the sense that the only exclusion criteria for participation were related to ethical considerations, such as the participants’ mental and physical well-being. Face-to-face interviews resulted in a low prevalence of missing data.
Attrition at T0 was mainly due to logistical challenges at the recruiting treatment sites (lack of resources among staff), still some of the most severe cases of substance use and dual diagnoses were not included in the study. Attrition at T1 was mainly due to the research group not reaching the participants (due to lack of updated contact information) or participants declining to participate. Agreeing to a follow-up interview was not an inclusion criterion at baseline. We cannot completely rule out that selection bias at T0 or T1 could have affected our results, we are however encouraged by two factors: First, sensitivity analyses detected no baseline differences between those included at follow-up and those lost to follow-up in demographics and the relevant variables for the analyses of this study. The only exception was that included participants reported a higher number of criminal acts at baseline, which is the opposite of what we would have expected if there was a serious selection bias favouring better-functioning participants at T1. Second, a methodologically relevant study of substance users (
n = 654) found that results based on the 60% of the sample that were
easiest to reach at follow-up were comparable to results based on 90–100% of the sample [
36]. Taken together, this gives us the confidence to consider the study sample to be nationally representative of patients enrolled in inpatient treatment or OMT in Norway. We consider the results to be relevant for similar patient populations and settings.
Self-reported data on criminal activity have been found to be reliable [
67‐
69]. Self-reported crime may have an advantage over use of official records that only reflect the instances where individuals were apprehended or convicted, and not the criminal acts they committed without these consequences [
16,
67,
68].
The additional regression analysis comparing the no crime and continued crime groups should be interpreted with care. The total n in the comparison was low (n = 92) and the wide confidence intervals show that the estimates are uncertain.
For the additional measure of type and number of crimes, the assessed time-periods at baseline and follow-up differed (6 and 12 months). When reporting number of criminal acts, the difference in time-periods was addressed by calculating the average monthly acts before baseline and follow-up.