Psychological Medicine

Original Articles

Internet cognitive behavioural therapy for mixed anxiety and depression: a randomized controlled trial and evidence of effectiveness in primary care

J. M. Newbya1 c1 p1, A. Mackenziea1, A. D. Williamsa1, K. McIntyrea1, S. Wattsa1, N. Wonga1 and G. Andrewsa1

a1 Clinical Research Unit for Anxiety and Depression, School of Psychiatry, University of New South Wales at St Vincent's Hospital, Darlinghurst, NSW, Australia


Background Major depressive disorder (MDD) and generalized anxiety disorder (GAD) have the highest co-morbidity rates within the internalizing disorders cluster, yet no Internet-based cognitive behavioural therapy (iCBT) programme exists for their combined treatment.

Method We designed a six-lesson therapist-assisted iCBT programme for mixed anxiety and depression. Study 1 was a randomized controlled trial (RCT) comparing the iCBT programme (n = 46) versus wait-list control (WLC; n = 53) for patients diagnosed by structured clinical interview with MDD, GAD or co-morbid GAD/MDD. Primary outcome measures were the Patient Health Questionnaire nine-item scale (depression), Generalized Anxiety Disorder seven-item scale (generalized anxiety), Kessler 10-item Psychological Distress scale (distress) and 12-item World Health Organization Disability Assessment Schedule II (disability). The iCBT group was followed up at 3 months post-treatment. In study 2, we investigated the adherence to, and efficacy of the same programme in a primary care setting, where patients (n = 136) completed the programme under the supervision of primary care clinicians.

Results The RCT showed that the iCBT programme was more effective than WLC, with large within- and between-groups effect sizes found (>0.8). Adherence was also high (89%), and gains were maintained at 3-month follow-up. In study 2 in primary care, adherence to the iCBT programme was low (41%), yet effect sizes were large (>0.8). Of the non-completers, 30% experienced benefit.

Conclusions Together, the results show that iCBT is effective and adherence is high in research settings, but there is a problem of adherence when translated into the ‘real world’. Future efforts need to be placed on developing improved adherence to iCBT in primary care settings.

(Received August 14 2012)

(Revised November 30 2012)

(Accepted January 08 2013)

(Online publication February 18 2013)

Key words

  • Anxiety;
  • cognitive behaviour therapy;
  • depression;
  • effectiveness;
  • Internet;
  • transdiagnostic treatments;
  • treatment outcome


c1 Address for correspondence: J. M. Newby, Ph.D., MRC Cognition and Brain Sciences Unit, 15 Chaucer Road, Cambridge CB2 7EF, UK. (Email:

p1 Present address: MRC Cognition and Brain Sciences Unit, Cambridge, UK