This study is among the few that have used a probability-based sample of sexual minority adults to examine early life stress, and it is, to our knowledge, the only one to date that has used the ACE scale. In addition to assessing multiple forms of abuse, the ACE scale provides assessment of household dysfunction (i.e., familial mental illness, substance abuse, incarceration, parental discord, and domestic violence). These variables have been largely unexplored in the literature comparing the early life experiences of heterosexual and sexual minorities. This is among the first reports to show that in addition to abuse, sexual minorities may report higher rates of household dysfunction such as familial mental illness, substance abuse, incarceration, and for bisexuals, parental discord.
In support of our hypotheses, our results suggest that sexual minority individuals had increased odds of exposure to each of the majority of adverse childhood experiences, and they reported a significantly higher rate in the number
of adverse childhood experiences. This is particularly noteworthy in light of the evidence of the dose response relationship between adverse childhood experiences and poor health outcomes 
. Sexual minority populations experience numerous mental health disparities, such as depression, anxiety and suicidal behavior 
. Data about physical health disparities in sexual minority populations are limited, largely due to the lack of inclusion of sexual minority measures in population-based health surveillance surveys. However, disparities have been identified in asthma prevalence 
. It is unclear if adverse childhood experiences are major drivers of these disparities. In order to test causal explanations, it is crucial that future research focus on prospective studies that comprehensively measure variables such as gender nonconforming behavior, childhood adversity and the development of sexual orientation and sexual behavior over time.
The present findings on physical, sexual and emotional abuse corroborate literature outlining increased prevalence of these experiences among sexual minorities in comparison to heterosexuals 
. Specifically, sexual minority individuals in this sample had nearly twice the odds of experiencing physical, emotional and sexual abuse when compared to their heterosexual peers. Furthermore, by parsing gay/lesbian and bisexual groups, results indicated that bisexual individuals had almost three times the odds of experiencing sexual abuse than their heterosexual peers. This finding supports previous literature that suggests the examination of gay/lesbian and bisexual populations separately may be important for understanding particular experiences among each subgroup when comparing them to their heterosexual peers 
. For example, in this sample, lesbian/gay respondents did not differ from heterosexuals in reporting parental discord, whereas bisexual persons reported the highest prevalence. If lesbian/gay and bisexual persons had been combined into one group, that entire group would have seemingly reported higher prevalence of parental discord than the heterosexual group where the actual driver of the difference was only the bisexual group.
The etiology of these sexual orientation based disparities in childhood adversity is unclear. Some researchers posit that childhood adversity (particularly sexual abuse) may play a causal role in the development of same-sex preferences and or sexual minority identity 
. For many reasons, studies that suggest abuse or dysfunction causes minority sexual orientation may be less apt explanations for the higher prevalence of such reports. First, there is an empirical disconnect between prevalence of abuse and prevalence of lesbian, gay and bisexual (LGB) sexual orientation among the general population. For instance, research from nationally representative data shows the prevalence of ACEs to be quite high, with estimates ranging from greater than 50% of respondents endorsing one ACE, more than 25% of respondents reporting at least 2 ACEs, 30.1% reported being physically abused, and 19.9% reported sexual abuse 
. In terms of prevalence of LGB sexual orientation, the most recent nationally representative polling of the US population 
showed that only 3.4% of the population identified at lesbian, gay, bisexual (or transgender). If abuse or familial mental illness, substance abuse, incarceration, or domestic violence (either alone or in combination) caused a child to become lesbian, gay or bisexual, there should be a much higher percentage of the population identifying as LGB. Second, the studies are based on cross-sectional data, which precludes causal inference. Third, not all sexual minority individuals in the samples were abused (i.e., if abuse causes LGB sexual orientation, then all LGB people should have reported abuse). Lastly, these studies did not examine a key variable, namely gender nonconforming behavior, which may explain differential abuse among sexual minority persons.
Gender nonconforming behavior is behavior in opposition to societal gender norms (e.g., a male who takes ballet lessons, a female who wears men’s clothing). LGB persons are, arguably, gender nonconforming in the very nature of their attraction to persons of same sex. While gender nonconforming behavior is not necessarily an indication of childhood sexuality, it is associated with sexual orientation in adulthood 
. Moreover, gender nonconforming behaviors are often recognized by adults before a child is aware of a sexual identity 
. Evidence indicates that both adults and peer groups may resort to physical violence or abuse to censor gender nonconforming behavior or other indications of sexual minority status 
. In families experiencing dysfunction such as alcohol abuse and mental illness, a child with gender nonconforming behavior may more likely be targeted for abuse in this environment 
. Thus, rather than sexual abuse being causal of sexual orientation, unmeasured underlying factors, such as gender nonconforming behavior, may increase the likelihood of victimization of some children who later identify as a sexual minority 
Another explanation for increased reports of familial dysfunction by sexual minority populations is a willingness among LGB people to disclose private, stigmatizing, or delicate information. Findings from several studies reported that a majority of LGB participants had attended psychotherapy, which may increase an individual’s recognition of family dysfunction and comfort in disclosing ‘taboo’ information 
. Further, it is possible that, given the social stigma leveled against LGB identity, sexual minorities may spend considerable time reflecting on the meaning of identity, authenticity, and the ways in which developmental experiences may have shaped their lives 
. So, for instance, it is possible that bisexual individuals who have experienced parental separation or divorce may be more likely to identify as a sexual minority given that the strictures and scripts of heterosexual norms for marriage already have been removed or edited in their schemas, and they may feel comfortable publically expressing their identity.
The need to discern the etiology of such targeted violence against sexual minority individuals is made all the more important given that early victimization is a risk factor for victimization in adulthood 
. Combined with previous research, the current findings suggest that LGB youth may experience significant disadvantage early in their developmental trajectories given the higher prevalence of household dysfunction and familial victimization. This is to say nothing of the substantial evidence showing that sexual minority youth are more likely than their heterosexual peers to experience assault, abuse and bullying outside the home 
. The synergistic effects of familial and non-familial victimization among sexual minority populations are key areas for future research. Furthermore, there is a clear impetus for research about perpetrators of violence against sexual minority persons. Data about victimization come largely from victims’ self-reports, but the actual reasons for why
a sexual minority person was selected for victimization lie more clearly with the perpetrator(s) of the acts.
Several limitations must be noted. First, despite being a large probability-based sample, the analyses are based on data from three states, which limits generalizability. Moreover, because the data were pooled across three states that administered the ACE scale to varying proportions of their total sample (e.g., sample splits or specific counties within sample splits), sample weights were not used. BRFSS sampling methodology may result in different forms of bias, such as the lack of inclusion of institutionalized persons and the inability to survey persons who have only cellular telephones and not a landline household phone. The self-identity measure of sexual orientation may introduce selection bias, in that the measure typically identifies respondents who are willing to disclose their sexual orientation. The average age of respondents in this study was in middle adulthood, so there may have been recall bias in reporting ACE items from before the age of 18. Furthermore, there may be unidentified cohort effects of how people disclose certain ACE. For example, for middle-aged adult respondents, parental discord may be more taboo given the era in which they grew up, versus young adult respondents who grew up in later decades when parental discord was more prevalent. Lastly, the sample size of sexual minority persons did not permit analyses to specifically examine gender and racial/ethnic minority groups.
In spite of these limitations, this study is currently one of the largest to examine multiple adverse childhood experiences in a probability-based sample of sexual minority adults and the only study to use the ACE scale. A benefit of this widely used ACE scale is that it contains multiple risk factors in addition to childhood sexual and physical abuse that may contribute to health outcomes. Including the ACE scale in future research among sexual minority individuals constitutes a valuable measure of developmental risk factors. While research is clearly needed to examine the longitudinal consequences of childhood adversity among sexual minority populations, there is an equal, if not more pressing imperative to prevent the maltreatment of sexual minority children and youth.