When I have been stressed out for longer periods of time, I start to get weird problems with sleep. This has included hearing many indistinct voices when going to sleep, waking up to a sleep paralysis with the demon sitting on me / next to me, and sensation of falling immediately after falling asleep (which makes it impossible to sleep). In all of the cases, it seems like the unconsciousness is so occupied that it doesn't want me to rest. Every time, when I have talked about my worries hence processed them, the symptoms have gone away. So to at least to my anecdotal experience, the sleep disorders seem to be caused by held back emotions.