A randomized controlled trial of internet-delivered cognitive behaviour therapy to prevent the development of depressive disorders in older adults with multimorbidity

•The first investigation of internet-delivered cognitive behaviour therapy for preventing depression in older adults with multimorbidity.•Internet-delivered cognitive behaviour therapy was effective in preventing depression at six-month follow-up.•Despite very low mean depressive scores at baseline, there was still a significant reduction in symptoms by post-intervention compared to controls.•Longer follow-up is required to conclude whether the preventative effect of internet-delivered cognitive behaviour therapy is sustained. Multimorbidity, which commonly impacts older adults is associated with higher rates of depression. We aimed to investigate whether internet delivered cognitive-behaviour therapy (iCBT) could prevent depressive disorders in older adults with multimorbidity who were not currently depressed. 302 primary care and community participants aged 65 years and over, who had multimorbidity but did not meet criteria for a depressive disorder were randomised to an intervention group who received an eight-week, five session iCBT (n = 150) or to a control group (n = 152) who received treatment as usual. Diagnostic interviews were conducted at baseline, and three and six months after the intervention period, where indicated, and the presence of depressive disorder was the primary outcome. The intention to treat, chi-square analyses indicated there were significantly fewer cases of depressive disorder in the treatment group compared to the control group by six-month follow-up (χ²(1,302) = 5.21, p = .02). The main limitations of this RCT are a short follow up period and low proportion of participants who developed depressive disorders. Participants were relatively well educated, with a majority having English as their first language. These results indicate that depressive disorder was prevented in the first six months following iCBT with three times the number of cases of depressive disorder in the control group compared to the treatment group. Further research is required to determine whether iCBT can be effective for preventing depressive disorder in this population over a longer time period.