The Self-help Online Against Suicidal Thoughts (SOS) Trial

The objective of the SOS-trial is to examine if an online self-help intervention is effective in reducing suicidal thoughts among people at risk of suicide. The SOS-trial is a randomized, wait-list controlled trial with 1:1 allocation ratio. A total of 438 people with suicidal thoughts will be allocated to the intervention condition (N=219) or the control condition (N=219). The intervention condition consists of a six-week internet-based self-help therapy intervention. The control condition consists of a waiting list assignment for 32 weeks. The primary hypothesis is that the intervention is superior to the control condition in reducing suicidal thoughts at post-test (6 weeks). The SOS-trial is a partial replication of a previously conducted Dutch trial.

Suicide accounts for over 800,000 deaths each year and suicidal thoughts are common and cause distress for millions of people over the world.

With this study, the investigators wish to examine the effectiveness of an online self-help intervention in reducing suicidal thoughts among people at risk of suicide.

The participants will be recruited through the Danish online and telephone service, the Lifeline's website. Persons who consent to participate in the study will be randomized to the intervention or control condition using a centralized and computer-based algorithm that is stratified by sex and level of suicidal ideation. The intervention consists of an online self-help program with six modules that each takes a week to complete. Every module has a theoretical section, a compulsory exercise, and several optional exercises. The participants will be encouraged to spend a minimum of 30 minutes every day with the self-help program. The participants in the control condition will have access to the website but not the intervention modules.

Measurements with self-report questionnaires will be carried out at baseline and after 2, 4, 6, and 32 weeks. The participants in the control condition, will after 6 months on the waiting list mode assessment have access to the intervention. These participants will further be assessed 3 times, i.e. after 34, 36 and 38 weeks.

The null-hypothesis assumption of no difference between the intervention and control condition with respect to suicidal thoughts and the secondary outcome measures will be tested. Mixed models will be used to assess changes over time in suicidal thoughts and level of depression, with the measurements at baseline, 2, 4, and 6 weeks (post-test) as well as the long-term effect at 32 weeks (6 months after post-test). Changes in secondary outcomes will, apart from the participant's depression level, be measured with ANCOVA using multiple imputations. The investigators will use Cohen's d test to determine the difference between the intervention and control condition.

If the true difference in the experimental and control mean is 0.3 in the Danish trial and a pooled standard deviation at post-test at 1 is expected, then 350 participants in each condition is needed in order to reject the null hypothesis that there is no difference between the intervention and control condition at post-test on suicidal thoughts with probability (power) 0.8. The type I error probability associated with this test of the null hypothesis is 0.05. By accounting for a drop-out rate of 20%, a total of 438 participants will be needed in the SOS-trial.

The participants constitute a vulnerable group, and a safety procedure has therefore been developed. Participants will only be included if they provide their telephone number and the number of a contact person upon enrollment. During the first 6 weeks of the trial, the Beck Scale for Suicide Ideation will be administered biweekly; if a participant in either the intervention or control condition scores ≥ 27 on the scale, he or she will receive a telephone call from the trial manager. If the participant cannot be reached during three attempts over three days, the participant's contact person will be contacted. The same procedure will be used out if a participant ceases to follow the intervention without notifying the trial manager.

Eligibility Criteria:
Inclusion Criteria:

* Age above 18 years old
* Have a personal code card (NemID)
* Sufficient command of the Danish language

Exclusion Criteria:

* No suicidal thoughts (defined as a score below 3 on the Beck Scale for Suicide Ideation).