An unpleasant experience of an emotional, psychological, social, or spiritual nature that interferes with the ability to cope (e.g., cancer treatment).
It extends along a continuum, from common normal feelings of vulnerability, sadness, and fears, to problems that are disabling, such as true depression, anxiety, panic, and feeling isolated or in a spiritual crisis.

National Cancer Institute (NCI). Managing emotional effects. Internet. Accessed on July 6, 2016.