Marijuana Use by Intimate Partners: Does Discrepant Use Impair Relationship Functioning?

Intimate couples with discrepant use of alcohol and other drugs experience poorer relationship functioning relative to couples with concordant use or nonuse. Within a sample of marijuana-using couples, we hypothesized that greater discrepancy in marijuana use frequency between partners would be associated with lower relationship satisfaction and perceived partner responsiveness and with greater conflict, negative interpersonal exchange, and psychological and physical aggression. The Actor Partner Interdependence Model (APIM) allowed us to account for the effects of each partner's marijuana use, as well as the discrepancy between partners' use, on his or her own perceptions of relationship functioning. Using multivariate, two-level models, we considered both between-couple and within-couple effects of partner marijuana discrepancy using 4 waves of data collected over 10 months. The sample consisted of heterosexual community couples (ages 18-30) in which at least one partner reported using marijuana two or more times per week. For several outcome measures, we observed negative within-couple discrepancy effects on reports of relationship functioning: at time points when absolute discrepancy in marijuana use was greater than typical for the couple, relationship functioning was poorer. The pattern was the same regardless of whether it was the male or female partner who used more frequently. There were also some negative between-couple effects associated with more frequent female use. Findings replicate and extend prior research on partner discrepancy by demonstrating the dynamic nature of these effects over time.