Randomized Controlled Trial of Comet Via the Internet or in Group Format.

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Brief Title

Randomized Controlled Trial of Comet Via the Internet or in Group Format.

Official Title

Parent Training Targeting Externalizing Behaviors in Children in Primary Care: A Randomized Non-inferiority Study of the Comet-program Delivered Via the Internet or in Group Format.

Brief Summary

      The Comet-program is a Swedish parent training program developed to target externalizing
      behaviors in children between 3-11 years. The program is normally delivered in group format
      in primary and specialized care and has already been evaluated in several studies. The
      internet-based version of the program has also been evaluated separately, but in this study
      the two formats will be directly compared in a randomized non-inferiority study. Parent
      ratings, child ratings as well as blinded clinical assessments will be conducted before the
      interventions, after the interventions (2-3 month after start of intervention), and at
      follow-up (12 mont after first assessment). The primary research question is: Will the
      internet-based format of Comet be at least as effective as the group format in reducing
      externalizing behaviors? Secondary research questions concern possible differential effects
      of the two formats on cost-effectiveness, parenting behaviors, parent mental health,
      applicability and consumer satisfaction, and the children's quality of life.

Detailed Description


      The Comet-program is a Swedish parent training program developed to target externalizing
      behaviors in children between 3-11 years. The program content is behaviorally oriented and
      the emphasis lies on increasing parenting behaviors that reinforces pro-social behaviors in
      children, as well as limiting the reinforcement of anti-social behaviors. The program is
      manualized and normally delivered in group format with parents to 6-8 children in each group.
      The group sessions (11 sessions á 2.5 hours) are led by two practitioners and include
      information, role-playing, and home-work exercises. The group format has been evaluated in
      two large randomized controlled studies. The effect sizes on child externalizing behaviors
      have been medium to large (Cohen´s d). Because of the evidence supporting Comet and other
      research supporting the effectiveness of similar behavioral parenting programs, Comet has
      been implemented in primary and specialized care in Sweden. A challenge in primary care is
      however the implementation costs related to the program (e.g., training of group leaders and
      the time each group leader need to invest in each patient). Therefore, Comet (or similar
      programs) are in practice used to a small extent in primary care, despite clear
      recommendations to offer such treatments for externalizing behaviors. A possible solution
      would be to offer an internet-based version of the program, which in two large randomized
      controlled trials have shown medium effect sizes on externalizing behaviors in children. In
      the internet-based version, the patients (parents) work online with seven modules over a
      period of nine weeks. Every module contains information, video-clips, quizzes and homework
      exercises. Every week the patient communicates with a therapist, that gives brief guidance
      and feedback online.

      The internet-based format of the program has however been implemented at a very small scale
      in regular care. One reason is probably reluctance on part of practitioners as well as
      patients in replacing face-to-face contact with online-contact. The management system used in
      health-care in Sweden is another obstacle, since only face-to-face contacts are included.
      Hence, the clinics are not financially compensated for any patient contacts online. To
      overcome these obstacles, the present study will compare the regular Comet program in group
      format to a modified version of the internet-based version. In the modified version, the
      online contact between the patient and the therapist will be replaced with three individual
      face-to-face sessions (45 min each). This will reduce the total amount of time invested per
      patient to 135 mins, compared to 410-550 mins per patient in the group format.

      Research questions:

      The primary research question in the study is: (1) Will the internet-based version of Comet
      be at least as effective as the group format in reducing externalizing behaviors in children?

      The secondary research questions will be to investigate if the two formats of Comet will
      differ in terms of: (2) cost effectiveness, (3) consumer satisfaction/applicability for
      patients as well as practitioners, (4) effects on parent behaviors and mental health, (5)
      effects on the quality of the relationship between parents and children, (6) effects on the
      quality of life experienced by the children, and (7) if the application of parenting
      strategies included in Comet mediates change in child externalizing behaviors.


      To investigate these research questions, parents seeking help in primary care clinics for
      externalizing behaviors in their child will be recruited to the study. Six clinics will be
      involved in recruitment of participants and offering the interventions. Clinical
      psychologists on every clinic will therefore be trained in both formats of the Comet program.

      Enrolled participants will be randomized at each clinic to either take part in the group
      format or the internet-based format of Comet. The participants randomized to the latter
      format will start their treatment as soon as they have completed the first assessment, while
      participants in the group format will have to wait for the scheduled group to start
      (generally within 1-3 months after enrollment and first assessment). The post assessment will
      take place when participants have completed the intervention and the follow-up assessment
      will be 12 months after the first assessment point. In addition, parents in each condition
      will answer a few questions on a weekly basis during their interventions.

      Assessments at pre, post and follow-up will include parent ratings of child behaviors, parent
      behaviors, parent mental health, and consumer satisfaction/applicability (only at post
      assessment). At pre and post assessment blinded clinicians will also make a diagnostic
      assessment of Oppositional Defiant Disorder (ODD) and Attention Deficit/Hyperactivity
      Disorder (ADHD) symptoms of the participating children. When the clinician meets the child
      for these assessments, the child will also be answering questions (structured interview)
      regarding their experienced quality of life. Finally, the psychologist involved in the
      treatments will continuously take notes in a log-book for each participant. The log-book will
      contain information on parent attendance, adherence and adverse events. A selection of the
      treating psychologists will also be interviewed to assess their experienced applicability of
      the two formats of Comet.

      The weekly questions will measure child externalizing behavior and the extent to which the
      parents have completed homework exercises (parenting strategies).

      Since the primary research question is if the internet-based version of Comet is at least as
      effective as the group format, the power calculation was based on non-inferiority design. The
      first step is to decide the non-inferiority margin, which is the least acceptable difference
      between the conditions in order to conclude that the internet-based version is non-inferior.
      A conventional method for deciding this margin is to use 50% of the effect sizes found in
      previous studies of the already established intervention. When applying this method for the
      primary outcome measure, the calculation showed that 134 participants were necessary to
      include in order to achieve a power of 0.80. In other words, if there is truly no difference
      between the group format and the internet-based format, then 134 patients are required to be
      80% sure that the lower limit of a one-sided 95% confidence interval (or equivalently a 90%
      two-sided confidence interval) will be above the non-inferiority limit.

      Most research question will be analyzed using methods from non-inferiority design, i.e.,
      analyzing the difference between adjusted means at post and follow-up with regard to the
      non-inferiority margin. Primarily, these analyses will be performed on participants who
      completed the interventions and assessments (per protocol), since intention-to-treat analyses
      reduces power and increase the risk falsely concluding non-inferiority.

      For the second research question (cost-effectiveness), the clinical significance in each
      condition will be calculated and compared (i.e., the proportion of participants that have
      "recovered", "improved", are "unchanged" or have "deteriorated). Thereafter, the cost per
      patient for each treatment will be calculated and used to achieve an estimate of cost per
      recovered/improved participant. This method has previously been applied in a
      cost-effectiveness analysis of Comet and other parenting programs.

      The analyses of practitioner satisfaction and experienced applicability will mainly be
      descriptive, due to lack of power (to few practitioners involved in treatment) and due to
      fact that part of the data is qualitative (interviews).

      Finally, the analyses of mediation (research question 7), will be analyzed using Latent
      Growth Curve Modeling, which is suitable for data that is measured repeatedly during an

Study Type


Primary Outcome

Eyberg Child Behavior Inventory (change in externalizing behaviors)

Secondary Outcome

 Parenting Young Children (change in parenting strategies)


Oppositional Defiant Disorder



Study Arms / Comparison Groups

 Comet in group format
Description:  The standard format of the intervention that is well established in primary and specialized care in Sweden. Parents receive the education/training in small groups led by two group leaders.


* Includes publications given by the data provider as well as publications identified by National Clinical Trials Identifier (NCT ID) in Medline.

Recruitment Information

Recruitment Status


Estimated Enrollment


Start Date

March 19, 2018

Completion Date

December 20, 2021

Primary Completion Date

November 20, 2020

Eligibility Criteria

        Inclusion Criteria:

          -  Primary reason for contact with health care is child externalizing behaviors.

        Exclusion Criteria:

          -  Not sufficiently fluent in written Swedish to be able to take part in an
             internet-based (text-based) intervention.

          -  No access to computer/ipad/phone

          -  Social problems that makes investigation or intervention from the social services




3 Years - 11 Years

Accepts Healthy Volunteers



Martin Forster, PhD, , 

Location Countries


Location Countries


Administrative Informations



Organization ID


Responsible Party

Principal Investigator

Study Sponsor

Karolinska Institutet


 Region Stockholm

Study Sponsor

Martin Forster, PhD, Principal Investigator, Karolinska Institutet

Verification Date

August 2021