Jo has been seeing a counselor to discuss her issues with anxiety and depression, which developed a few months after she moved to a new city for a job.

What is the most likely source of her anxiety and depression?

The most likely source of her anxiety and depression is precisely her change of life to a new city and her new jo. All the changes a situation like that can bring to someone can be a factor of distress that can affect a person's life.

Explanation:

People that experence anxiety and depression are most likley to aggravate whenever a big change happends, or a particular difficult situation presents. Jo developed these symptoms after she moved into the new city, which is a life changing experience. This situation can be a factor of distress.