Commentary on Carlon et al.: High hopes—Integrating positive psychological interventions into substance use disorder treatment

Abstract

Neurobehavioral models underscore the potential clinical relevance of positive psychological interventions (PPIs) in people who use substances [1, 2]. The hedonic model proposes that substance-induced increases in mesolimbic dopamine levels are linked to experiences of reward that serve a positive reinforcment for continued use [3]. Furthermore, because hypo-responsivity to reward and anhedonia are implicated in substance use disorder (SUD) etiology and maintenance [4], experiencing positive emotions is one primary motivation for using substances. PPIs could support more proactive responses to anhedonia to increase experiences of reward unrelated to substance use that, in turn, reduce the likelihood of the overlearned response of substance use. On the other hand, negative reinforcement models highlight that symptoms of withdrawal such as depression serve as triggers for substance use [5]. Evidence-based skills (e.g. gratitude and mindfulness) in PPIs that increase positive psychological outcomes in the broader population could assist with more effectively managing negative emotions as triggers for substance use [6].

A recent systematic review and meta-analysis by Carlon and colleagues [7] examined the efficacy of PPIs among people who use alcohol or other substances. There were small and nonsignificant effects of PPIs on increases in positive psychological outcomes and reductions in substance use across eight randomized controlled trials (RCTs). PPIs integrate various evidence-based skills aimed at improving positive psychological outcomes [7], which has strengths and limitations. On one hand, interventions that incorporate multiple skills, such as cognitive-behavioral therapy, could potentially yield larger effect sizes. At the same time, substantial variability in the PPIs tested across RCTs makes it difficult to determine their overall efficacy and identify which intervention component(s) are most beneficial. To address these limitations, future RCTs should develop a unified protocol for PPIs, leverage dismantling and multi-phase optimization strategy designs to determine the best combinations of components, and establish the dose of PPIs necessary to improve outcomes in diverse groups of people who use alcohol, tobacco, and other substances.

Identifying the underlying mechanisms of PPIs is essential for improving their effectiveness in reducing substance use. A significant challenge in interpreting findings across prior RCTs is the heterogeneity in the positive psychological outcomes assessed. Some RCTs assessed positive psychological traits such as resilience and optimism, which may be more difficult to change compared to state measures like positive emotions (e.g. happiness, gratitude). Guided by revised stress and coping theory [8] as well as the broaden and build model [9], positive emotions are thought to be key mechanisms through which PPIs may achieve beneficial outcomes. Future RCTs should use more nuanced assessments to better capture the role of positive emotions in reducing substance use [10]. Mediation analyses to determine the extent to which positive emotions and other positive psychological outcomes partially account for reductions in substance use also provide a direct test of theory-based mechanisms [11]. Moreover, integrating objective, neuroimmune measures into RCTs could enhance our understanding of moderators and mediators of PPIs effect on alterations in reward processing, decreases in stress reactivity, and reductions in substance use. Assessing resting-state fMRI and inflammation markers could provide critical insights into among whom and how PPIs could support reductions in substance use [12-14].

Although there is still much to learn about the efficacy of PPIs, they may be best conceptualized as an adjunctive approach that can facilitate SUD treatment initiation and retention, rather than as stand-alone interventions [15]. Most evidence-based SUD treatments use deficit-based, cognitive-behavioral or 12-step approaches that require patients to be ready, willing, and able to pursue abstinence. Although these evidence-based approaches are central to successful treatment, they are not reaching most people with a SUD [16, 17]. Because PPIs aim to improve positive psychological outcomes without directly addressing substance use, they offer a feasible and acceptable approach for engaging a broader population of people who use substances regardless of whether they are currently seeking or receiving formal SUD treatment.

Even though there is not sufficient evidence regarding the efficacy of PPIs, their promise as a low-threshold, complementary approach for people who use substances warrants further exploration. More rigorous RCTs are needed to address the substantial variability in intervention protocols and positive psychological outcomes examined. These RCTs should also aim to clarify the psychological and neuroimmune mechanisms through which PPIs might reduce substance use. In conclusion, more concerted efforts are needed to establish whether, how, among whom, and under what conditions PPIs could reduce in alcohol, tobacco, and other substance use. There are high hopes that PPIs have the potential to offer valuable adjunctive support, particularly those who are not currently seeking or engaging in formal SUD treatment.

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