Please refer to the video below from The Curious Classroom, to ensure that you have a good understanding of stress response:

Studies determined that there is a close relationship between stress response (i.e. release of cortisol) and stereotypic behaviors(Bachmann et al., 2003). So if an animal is in an environment that induces stress, then the animal will most likely express stereotypical behaviors (Bachmann et al., 2003)

Relation with Welfare: 

Stress can have long term negative effects on the animal’s body, leading to overall poor health conditions and poor welfare of the animal (Fraser, 2008).