Relationships between self-harm and vulnerability factors were studied in a general population of 432 participants, of whom 30% reported some experience of self-harm. This group scored higher on dissociation and childhood trauma, had lower self-worth, and reported more negative intrusive thoughts. Among the non-harming group, 10% scored similarly to the self-harmers on the dissociation and self-worth scales, and engaged in potentially maladaptive behaviors that are not defined as indicating clinical self-harm, but experienced fewer negative intrusive thoughts. This group may be at risk of future self-harm if they begin to experience negative intrusive thoughts. If negative intrusive thoughts are playing a causal role, then therapeutic approaches tackling them may help those who are currently self-harming.