I don't know whether it would be classified as MCI, but I found that after my husband died, I experienced an existential vacumn= loss of purpose. Difficulty concentrating, couldn't remember how to get to places in town, forgot people's names, finishing things, wanting to be alone, all thoughts of the future were bleak. Reading & volunteering has helped somewhat. I don't want to socialize but being with other people has helped......maybe because it takes you out of yourself for a bit.