The findings of this study provide empirical support for the effectiveness of a self-help manual in strengthening resilience in individuals with moderate depression. However, the findings presented here need to be assessed alongside data presented elsewhere from this study on depression  and psychological distress .
The findings suggest that a significantly greater improvement in resilience was observed in adult participants with moderate depression who received the bibliotherapy self-help manual than in those who only received the standard care and treatment approach to living with depression. These differences were apparent from baseline to post treatment, and the treatment effects were maintained at 1-month follow-up. Although both groups showed improvements in resilience throughout, the intervention group exhibited a more pronounced improvement than the control group. Overall, the differences between the two groups may be attributable to the beneficial effects of the bibliotherapy manual in enhancing resilience in the intervention group participants with depression. These findings are consistent with systematic reviews and meta-analyses which highlight the benefits of bibliotherapy for depression [12, 16, 42].
While few studies of bibliotherapy for depression have been conducted in Asian countries, the findings of the present study show that the approach can produce positive outcomes in a Thai context. The findings are similar to those of Liu et al. , who reported that bibliotherapy was an effective intervention for adult Chinese people with depression in Taiwan. Overall, both studies affirm that bibliotherapy is an effective approach for the treatment of depression in Asian countries.
Although statistical significance was reported in the present study, several culturally relevant factors should be taken into consideration. The finding of improved resilience in both groups may be attributable, in part, to the influence of family support in a Thai cultural context. Although resilience is considered usually an individual characteristic , adaptive functioning in the face of adversity is dependent not only on individual characteristics but is affected by processes and interactions arising within the family and from the immediate social environment . Social support and meaningful relationships with at least one peer or family member are consistent with good resilient outcomes , and contribute positively to overall well-being.
Overall, while the standard care and treatment approach and Thai cultural context may have had a positive influence on improving resilience in both groups, the intervention group participants exhibited greater improvement than those in the control group. A possible favourable effect of the bibliotherapy programme is that through improvement in resilience the participants also developed positive emotions, which, in turn, helped them deal with their depression. This finding is consistent with the results of several studies that examined the role of positive emotions in the promotion of resilience [21, 22]. Moreover, people with high levels of resilience are likely to show low levels of depression . Bibliotherapy is suitable for people with moderate depression, but is unsuitable for individuals with severe depression  because of marked difficulties in concentrating and cognitive impairment, and a greater suicide risk . The approach must be monitored carefully by clinicians, however, as misinterpretation of information can aggravate symptoms, particularly among people with depression who are withdrawn socially . This precautionary strategy is consistent with the approach used in the present study, where weekly telephone calls were made to support and encourage intervention group participants to complete the programme. The benefits of weekly contact were similar to those reported in the Cuijpers  study, which found that bibliotherapy programme participants benefited from weekly telephone contact with a health professional.
There are several advantages to using bibliotherapy as an adjunct to standard treatment in this type of depression. The approach provides specific techniques and homework exercises which participants are encouraged to carry out between sessions, to challenge unhelpful thoughts and behaviours and to enhance their resilience. Bibliotherapy also may help maintain treatment gains because individuals can readily revisit strategies at later points in time. Self-monitoring and self-assessment can assist individuals to assess treatment gains and to alert them about potential problems and the need to consult clinicians. Bibliotherapy also may reduce negative emotions and stigma associated with seeking traditional approaches to care and treatment [3, 49–51]. It is a cost-effective approach based on CBT, and is more convenient, less expensive, more widely and easily accessible and portable than standard and specialised treatment modalities [15, 49], especially in a Thai context where affected individuals may have to travel considerable distances to outpatient departments and pay for treatment.
There are limitations to using bibliotherapy. The modest effect sizes obtained (small-to-medium) in the present study might have been attributable, in part, to the brief telephone support that was provided. It is noteworthy in the Phipps et al. study  that while the brief contact and the assisted self-help intervention groups had significant reductions in depression and psychological distress compared with the control group, the assisted self-help group, who received more support than the brief contact group, showed the greatest level of symptom reduction. Thus, it could be interpreted that Thai people in this study might have a preference for a greater balance between bibliotherapy and direct contact with a clinician. This is some justification for this inference as most Thai people, particularly adolescents and adults, dislike reading, preferring to listen to information presented on the radio and watching television (Thai National Statistics Organisation . This contrasts with, for instance, Australia, where most people regard reading as a pleasurable activity, and read newspapers, magazines and books at least once a week .
In terms of treatment adherence, the adherence rate in the current study compares favourably with that in the Liu et al.  study in Taiwan, which reported their participants read an average of 7.83 (SD = 2.99) chapters out of 10. The difference in the adherence rates for the reading and written parts of the manual in the present study may be due to some participants having difficulties with, or being reluctant to complete, the written but not the reading component. The finding about re-reading has also been reported by Scogin et al. , who found that almost 50% of participants re-read parts of their book after finishing the study. It is noteworthy, however, that re-reading was not reported by Bilich et al.  in their study of the Australian version of the bibliotherapy manual used in the current study.
Limitations and strengths
There are several limitations to the study. Recruitment through the outpatient department means that the results may not be generalisable to other people with depression in the community who do not attend this department. The assessor of the self-report outcome measure was not blinded to the allocation of participants to each group. In our view, while this did not have an adverse effect on the findings, it is, nevertheless, a potential limitation. Furthermore, the subjective nature of the measure could be conceived as a limitation. The study was also limited by the 4-week timeframe between post-test and follow-up. In addition, the generalisabilty of the findings is limited to participants who have some reading and writing ability, and bibliotherapy may not be suitable for everyone with moderate depression, particularly those with lack of energy and poor concentration [7, 47].
The study has two strengths: it's randomised control trial parallel group design and high retention rate. We used this design to evaluate an intervention in a clinical population and cultural context that has been under-represented in previous bibliotherapy studies of individuals with depression, and were able to demonstrate significant improvements is resilience following the intervention. The retention rate in our study (96.4%) was much higher than the Australian study that used the manual (63%) . Cultural differences between the two countries and the use of the short weekly telephone contact for both groups might have contributed favourably to the high retention rate in our study.