Name of Specific Agency Responsible for Content. (Date). Title of webpage. Add names of parent agencies if available. URL
Often times, these webpages do not have individual authors, instead use the agency or company responsible for the information. If there is no obvious date, there may be a date last modified located near the end of the content. If neither are present, use n.d. for "no date".
National Institutes of Mental Health. (2018, March). Older adults and mental health. U.S. Department of Health and Human Services, National Institutes of Health. https://www.nimh.nih.gov/health/topics/older-adults-and-mental-health/index.shtml