This study investigates how giving and receiving support on an online forum for substance use disorders (SUDs) affects recovery, particularly focusing on how these effects are influenced by participants' self-efficacy. Analysis of 3440 messages from 231 participants revealed that receiving emotional support was linked to reduced illicit drug use over 6 and 12 months. For participants with low self-efficacy, giving emotional support was associated with decreased risky drinking, whereas giving informational support was linked to increased risky drinking.