Rates of drug use and dependence are generally higher among sexual minority men (SMM) compared to their heterosexual counterparts [12]. Across studies, the drugs most commonly reported include marijuana and a number of other illicit drugs, such as cocaine or crack, methamphetamine, ecstasy, ketamine, and/or gamma-hydroxybuterate (GHB) [1]. Therefore, the development of effective drug use interventions for SMM in relationships—including gay, bisexual and other men who have sex with men—is a public health priority.

In addition to the health risks inherent to drug use itself, drug use is a well-established correlate of sexual HIV transmission risk behavior. This is of substantial concern because SMM accounted for approximately 69% of all HIV diagnoses in the US in 2018 [3]. Earlier research indicated that 35–68% of new HIV infections among SMM were transmitted between main partners [4,5,6]. Estimated rates were as high as 79% among younger SMM (aged 18–29) [6]. More recent research has indicated that the likelihood of having condomless anal sex (CAS) with casual partners is comparable for single SMM and partnered SMM in non-monogamous sexual agreements [78]. Moreover, some evidence suggests that SMM in monogamous relationships who break their agreement and engage in CAS with casual partners may actually do so more frequently than non-monogamous and single men [7].

There is consistent evidence that associations between drug use and sexual HIV transmission risk behavior generalize to SMM in relationships. Several studies have demonstrated that the use of a number of illicit drugs is associated with the occurrence or frequency of CAS with casual partners [e.g., 912]. This association held across relationship status and sexual agreements, and was significantly stronger among single and non-monogamous SMM [7]. In addition, a day-level association between illicit drug use and CAS with casual partners has recently been observed in dyadic data from SMM couples [13].

Findings related to marijuana and sexual risk-taking are mixed [e.g., 91415]; but recent studies have demonstrated that marijuana is associated with a modest and statistically significant increase in the likelihood of CAS with casual partners above and beyond other illicit drug use [712]. This finding has also been replicated in dyadic day-level data from SMM couples [13]. The findings of Starks et al. [7] provide some context for previous equivocal results. They found that marijuana predicted only the occurrence—not the frequency—of CAS and that the association was significantly weaker among men in non-monogamous relationships. They concluded that marijuana should be viewed as relevant to sexual behavior while acknowledging that its effect size was modest compared to other illicit drugs.

Motivational Interviewing (MI) [16] has demonstrated efficacy to address a wide range of health risk behaviors when delivered to individuals [17,18,19]. Additionally, there is substantial evidence that this approach is effective at reducing substance use when delivered in one-on-one counseling formats [20]. It has even been used successfully to achieve reductions in substance use and CAS with casual partners among SMM specifically [1721]. Unfortunately, follow-up analyses from the Young Men’s Health Project indicated that SMM who were partnered at the time of intervention receipt may have benefited less from the individually-delivered MI intervention compared to SMM who are single [22].

Despite the general promise of MI-based interventions, their use with couples has been relatively rare. The studies performed to date generally viewed such work through the lens of a significant-other being involved as an adjunct participant in the substance use treatment of an identified client, with mixed results [23,24,25,26]. One of the challenges to implementing MI with couples is the absence of clear guidance for how providers should manage conflict in session and what providers should do when partners argue against change [27].

To address this challenge, Starks et al. [2829] drew on Interdependence Theory [3031] to derive processes and techniques unique to implementing MI with couples. This work adopted the novel premise that the couple was “the client” rather than identifying one partner in the couple as “the client” and the other as an “adjunct participant.” This framework [2829] therefore provides a context for engaging couples where one or both partners in the relationship may use drugs to varying degrees.

Research informed by Interdependence Theory has shown that SMM in relationships use a variety of social control strategies to influence one another’s health behavior, including behaviors involving sexual HIV transmission risk and substance use [32]. Partners are more successful at working together towards a shared health goal when they are more satisfied with, invested in and committed to their relationships. Interdependence Theory posits that this occurs because, when couples have better relationship functioning, partners are more likely to consider the consequences of their actions not just for themselves, but for their partner and their relationship overall. This motivates people to respond constructively in moments of conflict or disagreement [3334]. Among SMM specifically, relationship functioning is associated with the use of more positive (supportive) and fewer negative (aversive) social control techniques [32].

Building on these principles, Starks et al. [28] proposed that facilitating dyadic functioning is an essential process unique to MI with couples. MI traditionally conceives of four processes: engaging, focusing, evoking, and planning [16]. Starks et al. [28] suggested that facilitating dyadic functioning—a process characterized by eliciting the couple’s strengths, activating pro-social exchanges between partners, and problem-solving around sources of conflict—was an additional essential component. Through subsequent qualitative analysis of session data, we derived techniques providers can use to mitigate conflict and support constructive accommodation in session [29]. This creates the opportunity for joint goal formation and planning.

While promising, this initial work on dyadic MI [2829] is, thus far, formative. The goal of the current study was to evaluate the preliminary efficacy of a brief MI intervention for SMM couples based on this initial work. The previous decade has seen substantial energy directed towards the development of couples-based HIV prevention interventions. Couples HIV testing and counseling (CHTC) [3536]—a service in which partners discuss HIV prevention, establish a sexual agreement, learn their HIV status, and develop a shared HIV prevention plan—is now a standard of care in the US. In addition, psychoeducational interventions with designated attention to drug use and sexual risk-taking for SMM couples have demonstrated promise in reducing sexual transmission risk behavior [37,38,39].

The current study evaluates the potential of a novel MI intervention with couples, incorporating dyadic HIV testing into both conditions, to advance the field further. The primary hypothesis was that receipt of the MI condition would be associated with significant reductions in primary outcomes (frequency of illicit drug use and CAS with casual partners) and secondary outcomes (drug use related problems and frequency of marijuana use) relative to control. Secondarily, we examined the potential for baseline drug use frequency, drug use related problems, and CAS frequency to moderate treatment effects. These moderation analyses represent a post hoc preliminary examination of which couples are most likely to benefit from MI—a pernicious question in this area of research that is as yet unresolved. In addition, this is the first study to evaluate the potential efficacy of MI with couples using the methods and approach outlined by Starks et al. [2829]. This approach deviates from prior efforts by conceptualizing the couple—rather than an individual partner—as the identified client. The theoretical assumptions underlying the intervention would suggest that treatment efficacy may be a function of both partners’ use.