Background: older people coping with the impacts of living with multimorbidity are at increased risk of developing a depressive disorder.

Objective: this article reports the 24-month results of a randomised controlled trial of an internet-delivered cognitive behaviour therapy, which aimed to test whether depressive disorders could be prevented in this population.

Participants: community-based participants aged 65 years and over, who had two or more chronic physical health conditions and were assessed as having no current depressive disorder.

Methods: in total, 302 participants were randomised to an 8-week, five-lesson, internet-delivered intervention program (n = 150) or treatment as usual (TAU, n = 152). The primary outcomes were cases of depressive disorder, assessed post-intervention and at 3-month intervals throughout the trial, and depressive symptoms, assessed at pre-intervention, post-intervention, 6, 12 and 24 months following the intervention.

Results: there were significantly fewer cases of depressive disorder in the intervention group (n = 23, 15%) compared with the TAU group (n = 41, 27%) during the 24 months after the intervention (χ2(1, N = 302) = 6.13, P = 0.013, odds ratio = 0.490 [95% confidence interval: 0.277, 0.867]), representing a 44% reduction in cases of depressive disorder. No differences were found on depressive symptoms at 24-month follow-up. Internet-delivered cognitive behaviour therapy had high engagement and acceptability.

Conclusions: the results provide support that depressive disorders can be prevented in older people with multimorbidity through participation in internet-delivered cognitive behaviour therapy. With access to internet-delivered interventions in clinical care settings increasing, this has implications for older patient care where multimorbidity is extremely common.