SummaryIn this study, we investigated whether sleep disturbances were present in animals that were characterized as high trait anxious, as measured by behavioural tests (reactions to a human intruder and rubber snake). The aim was primarily to demonstrate that sleep could also be perturbed in high anxious marmosets, as they are in humans, hence lending face validity to the marmoset model of anxiety. Movement was measured over a 2 week period using Actiwatch, an accelerometer, attached to the neck chain of 90 monkeys. From this, we identified that were two, independent dimensions of sleep sleep quality and sleep length. We found that animals that slept shorter had greater daytime activity levels. Animals with poorer sleep quality took longer to fall into lowest levels of activity during the night. On the other hand, animals that slept longer became most active earlier during the day. We further investigated how sleep, daytime activity, and circadian rhythm variables were associated with high anxious trait monkeys. We found that animals that higher daytime activity and had shorter sleep length tended to be more anxious, as measured by reactions to a rubber snake. No association between anxiety and sleep quality was found in the marmosets. This suggested that in high anxious trait monkeys, marmosets took longer to fall asleep and displayed more movement during the day, but their sleep quality was unaffected. Finally, we investigated how cortisol and the serotonin system might be affect our sleep parameters. Since these systems influenced development of trait anxiety, they might be expected to influence sleep as well. We found that animals with high baseline cortisol as measured by hair analysis would also display longer times to fall asleep and higher daytime activity. Hence, high baseline cortisol influenced sleep length and daytime activity in the same direction as high trait anxiety. This supports that notion that cortisol might be an underlying influence to both trait anxiety and sleep. In our genotype analysis, we found that the G/A polymorphism for 5HT2A receptor and the AC/AC polymorphism for the 5HTT transporter both resulted in poorer sleep quality, while no such effect was found for sleep length. This suggests that the serotonin system primarily influences the sleep quality of the marmosets.