Assessment of medical morbidities in a rhesus monkey model of naturally occurring low sociality

Abstract

People with autism spectrum disorder (ASD) exhibit a variety of medical morbidities at significantly higher rates than the general population. Using an established monkey model of naturally occurring low sociality, we investigated whether lowsocial monkeys show an increased burden of medical morbidities compared to their high-social counterparts. We systematically reviewed the medical records of N = 152 (n = 73 low-social; n = 79 high-social) rhesus macaques (Macaca mulatta) to assess the number of traumatic injury, gastrointestinal, and inflammatory events, as well as the presence of rare medical conditions. Subjects' nonsocial scores, determined by the frequency they were observed in a nonsocial state (i.e., alone), and macaque Social Responsiveness Scale-Revised (mSRS-R) scores were also used to test whether individual differences in social functioning were related to medical morbidity burden. Medical morbidity type significantly differed by group, such that low-social monkeys incurred higher rates of traumatic injury compared to high-social monkeys. Nonsocial scores and mSRS-R scores also significantly and positively predicted traumatic injury rates, indicating that monkeys with the greatest social impairment were most impacted on this health measure. These findings from low-social monkeys are consistent with welldocumented evidence that people with ASD incur a greater number of traumatic injuries and receive more peer bullying than their neurotypical peers, and add to growing evidence for the face validity of this primate model. Lay Summary: People with autism exhibit multiple medical problems at higher rates than the general population. We conducted a comprehensive medical record review of monkeys that naturally exhibit differences in sociality and found that low-social monkeys are more susceptible to traumatic injuries than high-social monkeys. These results are consistent with reports that people with autism also incur greater traumatic injury and peer bullying and add to growing evidence for the validity of this monkey model.

Rhesus monkey sociality is stable across time and linked to variation in the initiation but not receipt of prosocial behavior

“…It is possible that, in an environment in which one's companions are relatively well-known, other mechanisms, such as avoidance, may mitigate the very real social deficiencies that have been demonstrated by low-social individuals (Capitanio, 1999(Capitanio, , 2002Capitanio et al, 2008). Nevertheless, in times of challenge, even in a familiar social environment, these social deficiencies may manifest themselves to an extent resulting in injury-as we have previously found (Myers et al, 2021). Clearly, more work is needed to understand the underlying psychological components of low sociality, and the contexts in which those components create social problems (and potential injuries) for the animals.…”

“…Possibly due to these inappropriate social responses, low-social monkeys also experience a higher rate of traumatic injury than highsocial monkeys (Myers et al, 2021). Thus, we hypothesized that lowsocial monkeys would initiate and receive a higher frequency of threat behavior compared to high-social monkeys.…”

“…Finally, although dependent on context, low‐social monkeys initiate more threats than high‐social monkeys early in group formations and in response to videos depicting unfamiliar animals displaying affiliative and aggressive behavior (Capitanio, 1999). Possibly due to these inappropriate social responses, low‐social monkeys also experience a higher rate of traumatic injury than high‐social monkeys (Myers et al, 2021). Thus, we hypothesized that low‐social monkeys would initiate and receive a higher frequency of threat behavior compared to high‐social monkeys.…”

Repeatability of measures of behavioral organization over two years in captive infant rhesus macaques, Macaca mulatta

“…Finally, we acknowledge that subjects might have underlying personality traits that covary with or contribute to the risk of hospitalization. For instance, prior work has shown that adult subjects that were more frequently observed alone in a social group had higher trauma rates relative to more social individuals, independent of rank (Myers et al, 2021); similarly, subjects with lower ratings on the macaque Social Responsiveness Scale-Revised had higher rates of trauma, relative to high rated subjects (Myers et al, 2021). Elfenbein et al (2016) also demonstrated that higher scores on the BBA Nervous temperament factor were associated with increased occurrences of diarrhea, relative to individuals with lower ratings.…”

Naturally occurring low sociality in female rhesus monkeys: A tractable model for autism or not?

“…Accordingly, we have used naturally occurring low sociality in male rhesus monkeys to model and study the social interaction impairments of ASD [ 5 ], focusing on behavioral phenotyping, biomarker discovery, and pharmacological testing. This work has determined that low-social males initiate fewer social interactions [ 6 , 7 ], show abnormalities in species-typical perception of, and responses to, social stimuli [ 8 , 9 ], exhibit a greater burden of autistic-like traits [ 10 ], and incur more traumatic injuries [ 11 ] than their socially competent male peers. Naturally occurring low sociality is also stable within individual males across time [ 7 ], unrelated to dominance rank [ 7 , 9 , 10 , 12 ], and highly heritable [ 12 ].…”