The effectiveness of peer support is believed to derive from a variety of psychosocial processes described best by Mark Salzer in 2002: social support, experiential knowledge, social learning theory, social comparison theory and the helper-therapy principle.
Social support is the existence of positive psychosocial interactions with others with whom there is mutual trust and concern. Positive relationships contribute to positive adjustment and buffer against stressors and adversities by offering (a) emotional support (esteem, attachment, and reassurance), (b) instrumental support (material goods and services), (c) companionship and (d) information support (advice, guidance, and feedback).
Experiential knowledge is specialized information and perspectives that people obtain from living through a particular experience such as substance abuse, a physical disability, chronic physical or mental illness, or a traumatic event such as combat, a natural disaster, domestic violence or a violent crime, sexual abuse, or imprisonment. Experiential knowledge tends to be unique and pragmatic and when shared contributes to solving problems and improving quality of life.
Social learning theory postulates that peers, because they have undergone and survived relevant experiences, are more credible role models for others. Interactions with peers who are successfully coping with their experiences or illness are more likely to result in positive behavior change.
Social comparison means that individuals are more comfortable interacting with others who share common characteristics with themselves, such as a psychiatric illness, in order to establish a sense of normalcy. By interacting with others who are perceived to be better than them, peers are given a sense of optimism and something to strive toward.
The helper-therapy principle proposes that there are four significant benefits to those who provide peer support: (a) increased sense of interpersonal competence as a result of making an impact on another person’s life; (b) development of a sense of equality in giving and taking between himself or herself and others; (c) helper gains new personally-relevant knowledge while helping; and (d) the helper receives social approval from the person they help, and others.