It is clear that Jan is depressed. The reason as to why this is the case could be some underlying factors that are beyond her control, some of which she might not be aware of. In the causal chain that makes a person feel sad and depressed begins with negative self comparison. Jan feels helpless and sad and this is the theory behind her troubles. This then means that her form of depression could be psychological in nature. Her emotions and thoughts may be playing tricks on her, leading her to feel like she does. Her anger is inward and is turned towards herself because it is not originating from outside forces. She seems to be stomaching some issues which are now beyond her control and they could be the reason behind her depression.
At times, the self comparison and benchmarking is not always the cause of depression, it is not clear whether Jan has got these symptoms and therefore it cannot be ruled out that her condition is characteristic of feelings of inadequacy and negativity towards herself. Her current behavior which is characterized by withdrawal characteristics is an indication that something is wrong with her. She has started to see life through a negative lens which consequently has affected her emotional stability. Psychological issues are seen at play here and they are the ones that seem to be playing a major role in causing her the depression.