Mutual support groups whose meetings take place in local community settings, usually on a weekly or monthly basis, enabling participants to have face-to-face contact with other people. In-person support groups generally have scheduled meeting times, closed membership and professional leadership; and may feature speakers and activities.

Mutual support groups that schedule virtual "meetings" via the Internet. Included are groups using video conferencing platforms like Zoom or Google Meet (which emulate a person-to-person meeting using real-time video and audio streaming), e-mail listserv groups (which distribute posted messages to participants via e-mail), bulletin/message boards (whose postings are restricted to people who register), newsgroups (whose postings are unrestricted and open) and chat groups (which permit real time discussion) that are devoted to providing support for participants around a particular issue. Internet support groups are generally available around the clock; and are convenient for people with limited mobility, serious health issues or transportation problems, who don't have time for face-to-face meetings, or who simply wish to maintain their privacy and remain anonymous. They may be the only option for individuals with rare disorders or other unusual problems who are unlikely to find enough people in their local area to form a support group. Internet support groups may be monitored by professionals, but most are not.

Mutual support groups whose members are people who have specific social or emotional concerns or mental illnesses. Families and friends may also be welcome. The groups meet in-person, by telephone or via the Internet; and provide an opportunity for participants to share information, practical tips for daily living and encouragement about issues related to their concerns.

An alteration in thinking, mood or behavior or some combination of those that either creates distress or interferes with people's relationships or their ability function.

A condition in which individuals have a diagnosed mental illness that interferes with their functioning in a substantial way in combination with a developmental disability. "Dual Diagnosis" was previously used in the U.S. to describe individuals with a combination of a diagnosed mental illness and a substance use disorder, and is seen by many as a synonym for "Co-Occurring Disorders" (YF-5000.1515).