The past decade has seen a proliferation of cognitive training intervention trials aimed at remediating or reversing substance-related cognitive deficits . However, their implementation into clinical practice is almost non-existent, despite promising results and now having more flexible, precise, engaging and convenient modes of delivery . Gathering more data in this still-developing area is essential to facilitate translation. Even the most widely tested training interventions, such as cognitive bias modification, need more data to fully appraise their benefit for addiction treatment . This section summarizes recent advances in CT, identifies limitations in the evidence base, and highlights priorities and directions for future research to bridge the gap between science and practice. Current CT approaches can be broadly divided into: general cognitive remediation, working memory training , inhibitory control training , and cognitive bias modification .In SUD, general cognitive remediation approaches such as cognitive enhancement therapy and cognitive remediation therapy aim to reduce substance use and craving by targeting EF and self-regulation. Cognitive remediation has been shown to improve cognition in domains of working memory , verbal memory, verbal learning, attention, and processing speed . Positive outcomes have also been shown to be associated with increased neuroplasticity in emotion regulation-related fronto-limbic networks in individuals with schizophrenia and co-morbid SUD . A recent study delivered 12 two-hour group sessions of clinician-guided CRT and computerized CT over 4 weeks to a sample of female residents completing residential rehabilitation and found significant improvements in EF, response inhibition, self-control,grow table and quality of life relative to treatment as usual. Similar research has reported comparable improvements in cognitive functioning following CRT and CET , and improved cognitive functioning has been associated with reduced substance use at 3- and 6-month follow-ups .
Importantly, CET and CRT also demonstrate preliminary efficacy for SUD patients with cognitive impairments. However, their duration, intensity, and high cognitive demand—coupled with a current paucity of large-scale, methodologically rigorous clinical trials—may currently preclude their widespread implementation in clinical settings. Another manualized therapist-assisted group intervention is Goal Management Training , which trains EF and sustained attention and emphasizes the transfer of these skills to goal-related tasks and projects in everyday life. When combined with mindfulness meditation, GMT has been found to significantly improve WM, response inhibition and decision making in alcohol and stimulant outpatients relative to TAUand more recently also in poly substance users in a therapeutic community . A meta-analysis of GMT more broadly concluded that it provides small to moderate improvements in EF which are consistently maintained at 1–6 month followups . As such, GMT is likely to be an effective candidate cognitive remediation approach for SUD treatment; however, substantially more research is needed to validate this assertion, particularly regarding the translation of cognitive improvements into improved substance use outcomes.The most widely researched EF training intervention, WMT requires participants to repeatedly manipulate and recall sequences of shapes and numbers through computerized tasks that become increasingly difficult over time . WMT aims to extend WM capacity, so individuals can better integrate, manipulate, and prioritize important information, with the aim of supporting more adaptive decision making that leads to reduced substance use . Relative to many other approaches, WMT is intensive, typically requiring 19–25 days of training and as such, retention is often poor . While WMT has been shown to lead to improvements in near transfer effects , there is limited evidence supporting far-transfer effects of WMT on other measures of EF and importantly, on substance related outcomes . Reduced alcohol consumption 1 month after training was reported following WMT in heavy drinkers , but most studies have failed to demonstrate or even measure changes in substance use . For example, non-treatment seekers with alcohol use disorder who were trained with Cogmed showed improved verbal memory but no clinically significant reductions in alcohol consumption or problem severity .
While a study of treatment-seekers improved WM and capacity to plan for the future on a delay discounting task, there was no measurement of substance use outcomes . Similarly, studies of methadone maintenance and cannabis have found no evidence of far-transfer effects , although Rass et al.showed WMT-related reductions in street drug use among methadone users. Other forms of WMT have reported similar near-transfer but not substanceuse-related findings with methamphetamine patients and a mixed group of substance use patients. As such, the greatest limitation in the WMT literature is the failure to consistently examine substance use outcomes and therefore there is insufficient evidence at this time to support the utility of WMT as an effective adjunctive treatment for SUD.Since deficits in inhibitory control are associated with increased drug use , ICT aims to bolster inhibitory control through the repeated practice of tasks [e.g., go/no-go , stop-signal task]. Such tasks require individuals to repeatedly inhibit prepotent motor responses to salient stimuli . In a seminal study, a beer-GNG task which trained heavily drinking students to inhibit responses to “beer” stimuli resulted in significantly reduced weekly alcohol intake relative to students trained towards “beer” stimuli . A recent RCT of 120 heavily drinking students found that a single session of either ICT or approach bias modificationled to significant reductions in alcohol consumption relative to matched controls . Similarly, Kilwein et al.found that a single session of ICT reduced alcohol consumption and alcohol approach tendencies in a small sample of heavily drinking men . Despite these promising findings, each of the aforementioned ICT studies used community samples, and it has not yet been established whether these results will generalise to treatment seekers. Two meta-analyses recently concluded that ICT leads to small but robust reductions in alcohol consumption immediately after training . Di Lemma and Field reported reduced alcohol consumption in a bogus taste test after a single session of ICT or cue-avoidance training . Others have observed reduced alcohol consumption 1 and 2 weeks after ICT . These findings highlight the promise of ICT though there remains a paucity of research assessing long-term drinking outcomes outside of laboratory settings. Future studies of ICT with clinical populations should consider testing multi-session approaches akin to WMT. To date, few studies have trialled multi-session ICT: One found it to be ineffective for heavily drinking individuals, while another found that 2 weeks of ICT resulted in modest reductions of alcohol consumption among individuals with AUDs, compared to WMT or a control condition .CBM aims to directly interrupt and modify automatic processes in response to appetitive cues. Attentional bias modification aims to modify the preferential allocation of attentional resources to drug cues by repeatedly shifting attention to neutral or positive cues and away from drug-related cues. Despite several null findings , significant effects have included the reduction of alcohol consumption in non-treatment seeking heavy or social drinkers . Among treatment seekers, five sessions of AtBM have been shown to significantly delay time to relapserelative to controls who received sham training .
Similarly, six sessions significantly reduced alcohol relapse rates at a one-year follow-up relative to a sham training condition in a sample of treatment seekers with AUD . Among methadone maintenance patients, AtBM reduced attentional bias to heroin-related words, temptations to use, and number of lapses relative to TAU . However, among individuals with cocaine use disorder, it failed to reduce attentional bias, craving, and cocaine use . Likewise, 12 sessions of AtBM vs. sham training during residential treatment for methamphetamine use disorder failed to reduce craving and preferences for methamphetamine images . A systematic review of alcohol, nicotine,vertical rack and opioid AtBM studies concluded that despite numerous negative findings in the literature, eight out of 10 multiple-session studies resulted in reduced addiction symptoms , but without concomitant reductions in attentional bias . Approach bias modification , which uses the Approach Avoidance Task, requires an avoidance response to drug cuesand an approach response to non-drug cues. Several trials have examined alcohol ApBM, with evidence that short-term abstinence is increased by up to 30% with four consecutive training sessions during inpatient withdrawal and by 8%–13% at 12-month follow-up . Alcohol ApBM has demonstrated relatively consistent, moderate reductions in drinking behavior when delivered to clinical populations , and it was even added to the German guidelines for the treatment of AUD . Early neuroimaging evidence has examined the neuroadaptations that occur pre-to-post-cognitive bias modification training. This work has focused on two samples of abstinent alcoholics undergoing an fMRI cue-reactivity task. Participants showed higher baseline reactivity to alcohol cues within the amygdala/nucleus accumbens and the medial prefrontal cortex, respectively . The same samples, following a 3-week implicit avoidance task , showed reduced amygdala and medial prefrontal reactivity . Notably, these brain changes were associated with reduced craving and approach bias to alcohol stimuli but not abstinence 12 months later. While preliminary, these findings suggest that neuroadaptations associated with cognitive bias modification have clinical relevance and warrant replication in larger SUD samples using robust, active placebo-controlled designs. To date, only one study has been published that trialled ApBM in an illicit drug-using sample of non-treatment-seeking adults with cannabis use disorder . Relative to sham-training, four sessions resulted in blunted cannabis cue-induced craving but not less cannabis use. Overall, evidence suggests that ApBM is associated with reduced approach bias and reduced consumption behaviors for alcohol, smoking, and unhealthy foods . Recently, six sessions of ApBM delivered to 1,405 alcohol-dependent patients significantly reduced alcohol relapse rates at a 1-year follow-up relative to a sham-training condition . However, as these reductions were also observed following AtBM and a combined AtBM and ApBM condition, the authors concluded that all active CBM training conditions had a small but robust long-term effect on relapse rates. Finally, a meta-analysis of alcohol and smoking CBM studies showed a small but significant effect on clinical outcomes for alcohol , but a lack of evidence that reduced approach bias led to improved outcomes .
This assertion was challenged by Wiers et al.who noted that the review conflated proof-of-principle lab-studies and clinical RCTs and different samples . Importantly, these populations likely have differences in motivation/awareness for receiving an intervention to reduce alcohol use, which could explain inconsistencies in the reported effectiveness of CBM across populations .Currently CBM, particularly ApBM, appears one of the most promising approaches for individuals seeking treatment for AUDs; however, its effectiveness for other drugs is yet to be established. The most extensively trialled CT approach is WMT, which has shown promising results in alcohol and stimulants users. However, its high cognitive demand, training intensity, and apparent lack of far-transfer effects limit its application to clinical populations. ICT holds much promise for reducing alcohol consumption in heavy drinkers, but requires testing in treatment-seekers. Finally, more intensive group based approaches such as CRT/CET and GMT may improve EF and quality of life; however, their impact on substance use outcomes remains largely untested. Synergistic approaches now warrant exploration. Indeed, a study that combined WMT and AtBM has shown promising feasibility and improved EF, though substance use outcomes were not assessed. It may also prove fruitful to adopt staggered CT approaches, capitalizing on the brain,s capacity to repair itself during withdrawal, early and later abstinence by strengthening cognitive control and dampening cue-reactivity , prior to engaging in more intensive and cognitively demanding but ecologically valid group training for more extensive remediation .While there may be logistical challenges to the adoption of CT in clinical practice , the main impediment to implementing CT in clinical practice is the absence of robust evidence for treatment success of any one particular approach. This is largely due to the vast heterogeneity of studies, particularly regarding differences in treatment settings, samples , cognitive intervention approaches, number and duration of training sessions, targeted mechanisms, targeted drugs of concern and varying primary outcome measures. Similarly, the absence of brief, ecologically valid, easily-administered measures of cognition precludes the identification of candidates who are most likely to benefit from CT . As such, the evidence base for CT remains hampered by the marked lack of studies on clinical populations,the counter-intuitive neglect of assessing relevant substance use outcomes,the lack of adequately-powered RCTs,the limitations of research designs,lack of attention to individual-level trajectories of cognitive improvements in relation to substance use and quality of life outcomes , and a simple focus on direct relations between cognitive deficits and outcomes without considering person and environmental mediators and moderators of this relation .