Background: A large proportion of primary care patients with mental ill-health do not
meet criteria for a manifest specific psychiatric disorder, but have subsyndromal mental
ill-health that nonetheless requires treatment. The available research litterature
regarding how to treat this patient group is scarce and the high demand for therapeutic
services in primary care typically leads to low treatment accessibility. One possible and
practical therapeutic solution is online transdiagnostic CBT, which draws on shared
underlying mechanisms and is resource-efficient. There is still clear limitations in its
evidence-base there is little data on how this method compares to primary care as usual
for this patient group.
Purpose and aims: The overall purpose of the current trial is to build evidence for an
accessible online transdiagnostic CBT for primary care patients with subsyndromal
mental-ill health. A randomized controlled trial will be conducted where adult primary
care patients with mental ill-health (but without manifest specific psychiatric disorder)
will receive online transdiagnostic CBT or care as usual.
The main aim (I) of the study is to investigate if online transdiagnostic CBT yields
superior symptomatic improvement compared to care-as-usual when given in a primary care
context to patients with subsyndromal mental ill-health. Secondary aims are to
investigate (II) if the treatment conditions are associated with improvement in quality
of life, functional impairment, and neuroticism (III) moderators of treatment outcome,
(IV) mediators of improvement, and (V) the cost-effectiveness (including effects on
sickness absence) of online transdiagnostic CBT compared to primary care-as-usual. Should
the trial fail to show a significant difference on the primary outcome, a secondary aim
will also be to (VI) investigate if online transdiagnostic CBT is non-inferior to primary
care as usual in reducing psychiatric symptoms.
Methods: This is a randomized controlled superiority trials where consecutively recruited
adult primary care patients (N=500) are allocated in a 1:1 ratio to Internet-delivered
transdiagnostic CBT or to primary care-as usual. This trial is part of larger project
comprising two twin randomized controlled trials that are conducted in parallel where the
difference between them is that the current trial will include patients with subsyndromal
mental ill-health whereas the other (separately registered with clinicaltrials.gov) will
include patients with a manifest psychiatric disorder.
Participants are consecutively recruited from the regular influx of primary care
patients. Gustavsberg Primary Health Care Center in Region Stockholm, Sweden, is the
basis, but additional primary care centers will be engaged to facilitate the recruitment
and treatment of participants. The investigators expect that 10 to 20 primary care
centers in Region Stockholm will be engaged for the recruitment and treatment of
participants.
Patients who seek help for common mental health problems will be asked if they are
interested in applying for the study. Those interested will undergo an assessment
interview with a licensed clinician where all inclusion criteria are checked.
Measurements: See section Outcome Measures.
Treatment conditions: See section Arms and Interventions.
Data analysis: Change in the primary outcome measure will be analyzed using mixed effects
linear regression. Fixed predictors in these analyses will be time, group and their
interaction effect while taking individual variation in baseline symptom levels and
change over time into account, i.e., random intercept and slope. Change from baseline to
10-week follow-up will be the primary endpoint. Power analyses show that to have 90%
power to detect an effect size of d=0.25 (α=.05), given a correlation between
measurements of 0.7, and an expected attrition of 15-20%, 250 participants will be needed
in each arm (total sample size N=500). Should the main analysis show that there is a
non-significant difference on the primary outcome, the investigators will conduct a
secondary analysis of whether online transdiagnostic CBT is non-inferior to primary
care-as-usual where the non-inferiority margin on the primary outcome is set to d=0.25,
i.e., the bound of the one-sided 95% confidence interval must be within this margin for
non-inferiority to be demonstrated. With 500 participants, 15-20% attrition, and a true
null effect of zero, the study will have approximately 80% power to detect
non-inferiority.