To the Editor:
I very much enjoyed the recent issue of Psychological Medicine, particularly the review of internet-based cognitive behaviour therapy (CBT) (Spek et al. Reference Spek, Cuijpers, Nyklíček, Riper, Keyzer and Pop2007).
I was surprised, however, that the authors did not mention the paper by Carlbring et al. (Reference Carlbring, Gunnarsdóttir, Hedensjö, Andersson, Ekselius and Furmark2007) or other studies of internet CBT that were ongoing when they wrote this paper. Additionally, while the search strategy is not described in detail, the authors appear to have used electronic filters that, in our experience, reduce sensitivity. We have stopped using such filters and commented on this (Mayo-Wilson & Montgomery, Reference Mayo-Wilson and Montgomery2006) after the publication of the Cochrane Review ‘Self-help and guided self-help for eating disorders’ (Perkins et al. Reference Perkins, Murphy, Schmidt and Williams2006).
Declaration of Interest
None.
The Authors' reply
We thank Mr Mayo-Wilson for raising the issue on how systematic and exhaustive our search was in our recent meta-analysis (Spek et al. Reference Spek, Cuijpers, Nyklíček, Riper, Keyzer and Pop2007) of internet-based interventions for mood and anxiety disorders.
They suggest that we have used electronic filters that, in their experience, reduce sensitivity. We have checked their protocol for a Cochrane review (Mayo-Wilson & Montgomery, Reference Mayo-Wilson and Montgomery2007), but could not discover in this protocol the details on how many studies were missed by using the described search strategies. We did notice, however, that they have limited their searches to the CCDAN Controlled Trials Register, which may be the reason why they did not identify all studies that met their inclusion criteria. In our study, we have searched multiple bibliographical databases, which reduces the risk of missing studies.
Although this may not be clear from our paper, we searched not only for internet-based treatment, but we looked at all studies regarding cognitive behaviour therapy for mood and anxiety disorders in PubMed (1990–February 2006), PsycINFO (1990–February 2006), and Social Science Citation Index. Moreover, we also searched for all studies on internet-based treatments, not limiting ourselves to cognitive behaviour therapy. We checked reference lists of retrieved papers, and of earlier reviews in the field (Ritterband et al. Reference Ritterband, Gonder-Frederick, Cox, Clifton, West and Borowitz2003; Andersson et al. Reference Andersson, Bergström, Carlbring and Lindefors2005; Tate & Zabinski, Reference Tate and Zabinski2004). Furthermore, we contacted the corresponding authors of all included papers to obtain information about any other published or unpublished studies they were aware of.
We have the opportunity to validate the results of our search strategies, through the data of two other systematic reviews. In one of these, an overview is given of all computer-aided psychotherapy (including internet-based treatments of mood and anxiety disorders) (Marks et al. Reference Marks, Cavanagh and Gega2007), and extensive searches were conducted to identify all studies in this field. Our group is currently working on a new systematic review of internet-based interventions for all health problems, for which new extensive searches have also been conducted. Neither of these two systematic reviews found studies that were missed in our meta-analysis published in Psychological Medicine.
Mayo-Wilson points at a study which they thought was missed by us (Carlbring et al. Reference Carlbring, Gunnarsdóttir, Hedensjö, Andersson, Ekselius and Furmark2007), but this study was published one year after the closing date of our searches.
We think, therefore, that our search strategies were correct and that we have not missed important studies in the field.
Declaration of Interest
None.
