How can major depression affect my interests in life?

Lower motivation. Symptoms of major depression often include sadness, withdrawal, difficulty concentrating, appetite/weight changes, fatigue, low energy, hopelessness, guilt feelings, and sleep difficulty. Depression can also distort the way events are perceived, resulting in negative self-perceptions and loss of interest in previously enjoyed activities.
Yes. One of the more common symptoms of depression is a loss of interest in usual activities. Often it is associated with a lack of satisfaction or pleasure from activities. These symptoms are temporary. They go away with recovery from depression.