If I were to tell you that lesbian, gay, and bisexual (LGB) persons are often excluded from scientific studies of romantic relationships, I doubt you would be surprised. However, the extremely high frequency with which this actually happens just might. Believe it or not, a new research review reveals that nearly 9 out of 10 relationship studies exclude sexual minority couples and, in an even bigger surprise, this trend doesn’t appear to be changing.

For this analysis, researchers focused on scientific literature published between 2002-2012 that was indexed in two major databases: PsycINFO and Medline. The search was restricted to studies published in the English language, that focused on romantic relationships, and that included at least one health-related outcome measure.

The search was limited in this way because the relationships literature is vast, but also because “there have been no substantiated physiological differences discovered between LGB and heterosexual individuals that would justify their exclusion from health research.” In other words, the authors wanted to focus on area of relationships research in which there wouldn’t be a sound theoretical reason for restricting samples to heterosexual persons (e.g., if you were studying certain aspects of reproduction).

The search was also limited to those articles that clearly stated whether non-heterosexual couples were recruited or excluded from recruitment. Studies that allowed LGB individuals to participate were categorized as “inclusive,” even if sexual minorities were ultimately excluded from the final analyses. Thus, “inclusive” really meant “recruitment inclusion.”

The results revealed that 88.7% of these studies explicitly excluded sexual minority couples from participating. Furthermore, exclusion rates were not significantly different in the early part of the decade (2002-2003) compared to the later part of the decade (2011-2012).

That said, the authors did find that the language used to talk about relationships appeared to change over the decade, such that inclusionary terminology (e.g., “partner,” “significant other”) because more common.

Put another way, scientists seemed to be describing their research in a more inclusive way without actually making their research itself more inclusive. I can’t help but be reminded here of a concept I teach about in my introduction to social psychology course called moral hypocrisy, which involves trying to give the appearance of being helpful without actually helping.

Another troubling finding from this study was that a large number of relationship studies (173) were identified in this literature search that did not even mention participants’ sexuality anywhere in the paper. This is strong evidence that relationship researchers all too often make assumptions about their participants. I should mention that heterosexuality isn't the only thing that's often assumed either--monogamy is frequently assumed as well.

Excluding sexual minorities from relationship research in which there isn’t a sound theoretical rationale for doing so is problematic on multiple levels. Not only does it continue to render this group invisible, but it also restricts the advancement of scientific knowledge.

In the next decade of relationship research, it is important that scientists work together to develop more inclusionary research practices and avoid bringing unfounded assumptions about participants and their relationships into the lab. In the end, it will ultimately help us to conduct better science that generalizes to more of the population.

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To learn more about this research, see: Andersen, J. P., & Zou, C. (2015). Exclusion of sexual minority couples from research. Health Science Journal, 9(6).

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