Humans possess a deeply embedded need to belong. Feeling loved and needed brings confidence and happiness. When the need to interact and belong is denied through stigmatisation, it can have disastrous consequences to the mental and even physical health of the stigmatised person. Stigmas have caused untold amounts of pain and death, but they can also be beneficial. Stigmas against child molesters and racists, for example, help protect the innocent. Only by knowing what stigmas are and how they work can they be used effectively.
External, or social, stigmas are communally defined. They usually function to solidify an "in" group by distinguishing people from an "out" group. Those with disfiguring or gruesome diseases like leprosy in ancient times or HIV today are often targets for social stigma. Stigmas are further attached to cheaters and those labelled as somehow different, like the mentally ill. External stigmas work through people avoiding contact and not even doing business with the stigmatised, treating them as inferior.
Stigmatised individuals often internalise a stigma they experience. The USAID pamphlet "Breaking The Cycle: Sigma, Discrimination, Internal Stigma, and HIV" depicts internal stigma as a three-part cycle: First, the person internalises the stigma, feels loss of control and accepts denigration. This leads to a self-perception of shame, guilt and fear, which leads to protective action, usually the individual avoiding others and living in isolation. Isolation makes her situation worse, and the cycle repeats.
Tribal stigmas are those passed on genetically, like race and ethnicity, or generationally, like religion. Although in all cases the stigmatised "other" is seen as inherently inferior, the reasons justifying this can take many forms. Many whites and other groups of people historically saw blacks and Hispanics as disease carriers and natives as barbarians. Others, especially during the era of Nazi Germany, viewed Jews as inherently evil and parasitic. Such attitudes often result in discrimination, enslavement or extermination of stigmatised groups.
For every type of stigma, the most effective cure is education. Anti-stigma advocates run campaigns to raise awareness of the struggles of the stigmatised in hopes of breaking down stereotypes and building empathy and support. Methods of advocacy run from student groups, to lobbying, to getting to know the stigmatised. A successful example is San Francisco-based Stamp Out Stigma, which sponsors an interactive panel of four to six speakers who have suffered mental illness that meet with audiences to share life stories and answer questions.