ATTACH in Denmark: A Feasibility Randomized Controlled Trial

As this is a feasibility trial, the primary aim is to assess feasibility rather than efficacy. We have therefore pre-defined three criteria that will guide our evaluation of whether a future large-scale trial is feasible:

• Inclusion proportion: At least 25% of eligible parents consent to participation and randomization.
• Compliance proportion: At least 50% of parents randomized to the ATTACH group complete ≥7 of 10 sessions.
• Completion proportion: At least 70% of randomized participants provide complete data on the primary clinical exploratory outcome at 5 months.

Parents are assessed for their mentalizing capacity using the Parental Insightfulness Assessment interview (IA). Parental insightfulness is defined as the capacity to see things from the child's point of view. The IA is conducted as follows: 1) Video recordings of parent and child interacting. 2) Reviewing 2x2 minute video segments with the parent while conducting the interview. 3) transcription and coding of interview. The interview procedure has been modified to be in accordance with the trial's videorecording procedures, which originally includes reviewing of three video segments, while for this trial, we will include two video segments. The IA consists of 10 different scales, each given a score on a 9-point scale (low to high). Based on the scale scores, the parent is classified into one of four categories: Positively Insightful; One-sided; Disengaged; or Mixed. However, for this study, we will use scale scores from 1 to 9 as the primary indication of parental mentalizing capacity

Parental reflective functioning will be assessed using the Parental Reflective Functioning Questionnaire (PRFQ) for parents of children from 1 to 5 years, while the infant version (PRFQ-I) is used for children aged 0-1 year. The PRFQ/I is a self-report questionnaire consisting of 18 and 15 items, respectively. Item are scored on a 7-point Likert scale, ranging from 1 (completely disagree) to 7 (completely agree). Each item corresponds to one of three subscales reflecting aspects of parental reflective functioning, i.e., Interest and Curiosity in the child's thoughts and feelings; Certainty about the child's mental states; and pre-mentalizing (a non-mentalizing stance). The PRFQ/I is included in an online survey.

To assess non-parenting specific reflective functioning, we will use the 8-item version of the Reflective Functioning Questionnaire (RFQ-8). Each item of the RFQ-8 is scored on a 7-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). The RFQ-8 is included in an online survey

Mind-Mindedness (MM) reflects the parent's tendency to treat the child as a psychological individual in term of how they describe their child from a mentalizing stance, i.e., the child's thoughts, feelings, intentions etc. We will use the representational measure of MM, using parental written descriptions of their child: In the beginning of the online survey, the parent is probed to "describe your child", which will be coded according to the standard procedures. The MM is included in an online survey

At the home-visit, a trial investigator instructs the parent to play with their child as they normally would for a total duration of seven minutes. If the child is seven months or older, the interaction includes a mild frustration episode after three minutes, lasting for one minute (parent is instructed to remove child's preferred toy and keep it away from child for one minute). This will be assessed using the method Coding Interactive Behavior, assessing mainly parental sensitivity. The CIB consist of 33 items, 18 related to parental behavior (e.g., acknowledging child signals); eight to the child's behavior (e.g., initiation), and five to the dyad (e.g., dyadic reciprocity), and, finally, two scales are on the lead-lag of the interaction (i.e., child- or parent-led). All items are rated on a scale ranging from 1 (representing the minimal level of the behavior) to 5 (representing the highest level), with the possibility of providing half points.

At the home visit, the trail investigator instructs the parent to pick a task from a pre-defined list, that they would like to teach their child (e.g., stack blocks or draw a circle on paper). The recording cannot be shorter than 2 minutes and no longer than 5 minutes. This will be coded using the Parent-Child Interaction Teaching Scale (PCITS). The PCITS is made up of 73 binary items organized into six subscales, four pertaining to the parent and two to the child: Caregiver's Sensitivity to Cues; Caregiver's Response to the Child's Distress; Caregiver's Social-Emotional Growth Fostering; Caregiver's Cognitive Growth Fostering; Child's Clarity of Cues; and, Child's Responsiveness to Caregiver. Each item is scored either "yes" or "no", depending on if the described behavior is present during the teaching episode.

We will use the Ages and Stages Questionnaire, 3rd edition (ASQ-3) to evaluate child global development. It consists of 30 items corresponding to different subscales of developmental domains, i.e., cognitive skills (communication, problem-solving, and personal-social) and motor skills (gross and fine). The ASQ-3 identifies children at risk for adverse mental health and development. While the ASQ-3 is developed as a self-report questionnaire, it will be administered by an investigator together with the parent and child at the data collection visit to strengthen validity of responses.

This will be assessed using the Child Behavior Checklist (CBCL) for Children Aged 1.5-5 years. The CBCL measures internalizing and externalizing problems as well as sleep difficulties and somatic problems. The CBCL consist of 99 items, each scored on a 3-point scale from 0=not true, 1=somewhat or sometimes true, 2=very true or often true), with higher scores indicating more dysfunction and problems. The CBCL is included in an online survey.

To assess parental depression we will use the Edinburgh Postnatal Depression Scale (EPDS). The EPDS is a 10-item self-report questionnaire, with each item scored from 0-3 (range 0-30). It is designed to screen for possible depression based on how the parent has been feeling within the past 7 days, with higher scores indicating higher levels of depressive mood. The EPDS is included in the online survey.

We will use the Parenting Stress Index Fourth Edition short Form (PSI-4-SF), which is a 36-item self-report questionnaire assessing parenting stress on three domains: Parental Distress, Parent-Child Dysfunctional Interaction, and Difficult Child, as well as a Total Stress score, with higher scores indicating higher parenting stress. Each item is scored on a 5-point Likert scale (from Strongly Agree to Strongly Disagree). Clinically significant cut-offs have been established. The PSI-4-SF is included in the online survey.

This will be assess by the Brief Resilience Scale (BRS), which consists of six items scored on a 5-point Likert Scale (from Strongly Disagree to Strongly Agree, range 6-30), with higher scores indicating more resilience and increased ability to bounce back from stress. The BRS is included in the online survey

To assess overall healthy functioning or dysfunction of intrafamilial relationships We will use the McMaster Family Assessment Device - Short Version (FAD). It is a 12 item self-report questionnaire, with each item scored on a 4-point Likert Scale ranging (from Completely Disagree to Completely Agree), with higher scores indicative of more dysfunction. The FAD is included in the online survey

One year after randomization, we will retrieve information from the family treatment units on the current support needs of the family. This is to assess whether the family has required additional or ongoing support, or whether their need for support has changed.