Gould and Clum (1993) conducted a meta-analysis of articles, published between 1970 and 1990, that examined the application of self-help, a method of SM, on behavioral change with minimal assistance from an expert. A total of 40 articles were included and topics ranged from subclinical to clinical issues. Results showed that the overall effect size (ES) of the self-help approach was 0.76 when calculated by Glass’s Δ, a strong effect by Wolf’s (1986) criteria. Follow-up results showed that the benefits of acquiring SM skills were
retained by participants even after intervention completion. Furthermore, the ES of these interventions was similar to that of therapist-assisted interventions, indicating that a self-modification approach can be an effective strategy in improving certain behaviors (Gould & Clum, 1993).