Effect of social familiarity on salivary cortisol and self-reports of social anxiety and stress in children with high functioning autism spectrum disorders.

Lopata et al. (2008) watched kids with high-functioning autism meet two kinds of peers. One peer was a friend they already knew. The other peer was a stranger. The team took spit samples to measure the stress hormone cortisol. They also asked each child how nervous or stressed they felt.

The design was simple: same child, same room, only the peer changed. The goal was to see if familiar faces calm the body and if kids can tell when their body is stressed.

Cortisol went up when the peer was unfamiliar, but stayed steady when the peer was familiar. Surprisingly, the kids' own stress ratings did not change between the two conditions. Their words said, 'I'm fine,' but their bodies said, 'I'm on alert.'

The link between saliva numbers and self-ratings was weak. A child might show high cortisol yet report low anxiety, or vice versa.

Duerden et al. (2012) seems to disagree: they found higher cortisol and slower recovery in autistic kids after a blood draw. The difference is the trigger. A needle is a physical threat, while a new peer is a social threat. Same diagnosis, different stressors, so both findings can be true.

Wuang et al. (2012) extend the story by adding a control group. They showed that neurotypical kids ramp cortisol up then down after social stress, whereas kids with HF-ASD stay elevated longer. This supports Christopher's warning that unfamiliar peers can keep the stress system running.

Neuhaus et al. (2016) conceptually replicate the familiarity effect using heart-rate instead of cortisol. They found autistic boys showed more sympathetic activation with familiar partners, not strangers. Together, the studies tell us the body notices who is in the room, but which system spikes depends on how you measure it.

For BCBAs, the takeaway is to treat 'friendly stranger' as a mild stressor. Start new social groups with tiny doses: five-minute parallel play, then exit. Pair new peers with highly preferred items so the brain tags the setting as safe. Finally, never trust 'I'm not stressed' alone; watch for flushed cheeks, rapid breathing, or later meltdowns. Use gradual exposure and reinforce calm behavior across several short visits until saliva and words both say, 'All clear.'